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M4

The Apple M4 is a family of ARM-based system on a chip (SoC) processors designed by Apple Inc., succeeding the M3 series in the company's Apple silicon lineup and marking the first use of second-generation 3-nanometer process technology for enhanced efficiency and performance. Introduced on May 7, 2024, with the redesigned iPad Pro, the M4 variants—including the base M4, M4 Pro, and M4 Max—feature up to 16-core CPUs combining performance and efficiency cores, up to 40-core GPUs with hardware-accelerated ray tracing, and a 16-core Neural Engine capable of 38 trillion operations per second to support Apple Intelligence and machine learning workloads. The base M4 chip includes a 9- or 10-core CPU (3 or 4 performance cores and 6 efficiency cores, depending on configuration) and a 10-core GPU, delivering up to 1.5 times the CPU performance of the while enabling up to four times faster rendering in professional applications like compared to the same predecessor. The M4 extends this with up to a 14-core CPU (up to 10 performance cores and 4 efficiency cores, with base at 12-core) and up to a 20-core GPU, offering up to 1.9 times the CPU speed of the and 75 percent more than the M3 Pro for demanding tasks such as geo-mapping. Meanwhile, the flagship M4 Max provides up to a 16-core CPU and 40-core GPU, with support for up to 128 GB of unified memory and performance up to 3.5 times faster than the Max in creative workflows, alongside an advanced media engine for decode acceleration. Key innovations across the M4 family include dynamic caching for GPU , mesh shading for complex graphics rendering, and a new display engine supporting the Ultra XDR display with higher brightness levels up to 1,600 nits for content. These chips power devices such as the 2024 (with base M4), the October 2024 (M4), the October 2024 (M4 and M4 Pro), the October 2024 lineup (across all variants), the March 2025 (base M4), and the March 2025 (M4 Max), where they enable up to 18 hours of battery life, up to 2 times faster performance than M1-equipped models in tasks like , and seamless integration with Apple Intelligence features for on-device processing. The M4 series emphasizes single-threaded CPU leadership, with its cores outperforming industry competitors in benchmarks, while supporting up to four external displays and connectivity for professional workflows.

Military

Firearms and ordnance

The M4 carbine is a 5.56×45mm NATO assault rifle developed by Colt in the 1980s as a lighter and more compact alternative to the M16 rifle, featuring a shorter barrel and overall length for improved maneuverability in close-quarters combat. Originating from the XM4 prototype tested in 1985 and refined through specifications issued in 1987, it incorporates over 80% parts commonality with the M16A2 for logistical efficiency. Key design elements include a 14.5-inch barrel, a collapsible fiberlite stock adjustable for different user sizes and firing positions, and a MIL-STD-1913 rail system for mounting optics and accessories; it is also compatible with the M203 grenade launcher for added versatility. The U.S. Army formally adopted the M4 in 1994, initially issuing it to specialized units such as platoon leaders and vehicle crews before designating it the standard infantry carbine in 2005. The M4 saw extensive combat deployment during the and , where its compact design proved advantageous for urban operations, vehicle-mounted engagements, and house-to-house fighting, though it faced criticism for reliability issues in dusty environments leading to upgrades like the M4A1 variant with full-automatic fire capability. Production of the M4 and its variants, primarily by and later , has exceeded 500,000 units by 2025, with ongoing procurements including up to 30,000 additional M4/M4A1 carbines authorized in early 2025 to sustain inventory amid transitions to next-generation rifles. As part of the program, the US Army began issuing the to replace the in units starting in 2024, with the first deliveries to operational units occurring in 2025. The , also known as the Super 90 M4, is an Italian-designed 12-gauge adopted by the U.S. Corps in 1999 as the MK101 Mod 0, later redesignated the M1014 Joint Service to replace older models like the Remington 870 and Mossberg 500. Developed in 1998 specifically for military trials, it employs Benelli's Auto-Regulating Gas-Operated (A.R.G.O.) system for reliable cycling with various ammunition types, including low-power loads, and features an 18.5-inch barrel for maneuverability, ghost-ring sights, and a configuration. Variants include the standard M1014 for use and civilian-legal versions with fixed stocks and modified chokes, all maintaining a 5+1 magazine capacity. The excelled in and breaching roles during Operations Enduring Freedom and Iraqi Freedom, where its durability in adverse conditions—such as sand and extreme temperatures—was validated through rigorous field testing. Initial production for the U.S. military totaled 20,000 units delivered starting in 1999, with the shotgun's 8-pound design and minimal maintenance requirements contributing to its status as a preferred tool for and non-lethal munitions deployment.

Armored vehicles and equipment

The was the primary used by the and its Allies during , serving as a versatile platform for armored operations across multiple theaters. Produced from February 1942 to June 1945, the M4 series totaled approximately 46,732 units, making it one of the most mass-produced tanks of the era. Its design emphasized reliability, ease of maintenance, and rapid production to meet the demands of global conflict, allowing it to equip armored divisions effectively despite initial vulnerabilities. Key variants of the M4 included the M4A1, which featured a cast upper for improved manufacturing consistency and ballistic resistance compared to the welded hull of the base M4. The M4A3 incorporated a GAA V-8 gasoline engine, enhancing mobility and power output, while the M4A3E2 "" was an up-armored variant with only 254 units built, featuring thicker frontal armor to support advances against fortified positions. The standard armament across most variants was the 75 mm M3 gun, capable of firing high-explosive and armor-piercing rounds, supplemented by coaxial and hull-mounted .30 machine guns and a .50 anti-aircraft machine gun on the roof. These configurations enabled the Sherman to engage enemy armor, provide direct fire support, and suppress , though early models struggled against heavier German tanks like the and due to relatively thin armor—typically 2 inches (50.8 mm) on the hull front and 3 inches (76 mm) on the front. The M4 Sherman played a pivotal role in Allied victories, first seeing combat in North Africa where its maneuverability suited open desert terrain during operations like the Battle of El Alamein in 1942. In the Italian campaign, it supported the invasion of Sicily in July 1943 and subsequent advances through rugged landscapes, providing mobile firepower for infantry assaults. During the Normandy landings in June 1944, Shermans spearheaded breakthroughs at battles such as Arracourt, where superior tactics compensated for armor shortcomings, and endured harsh conditions in the Battle of the Bulge later that year. Post-war, the M4 continued in U.S. service through the Korean War, where variants like the M4A3E8 faced North Korean T-34/85 tanks effectively, and was supplied to allies including Israel for use in conflicts like the 1948 Arab-Israeli War and beyond. Reliability issues with the M4 primarily stemmed from its armor vulnerability, prompting upgrades such as factory-applied 1-inch steel appliqué plates over ammunition storage to mitigate catastrophic ammunition cook-offs, and field modifications like sandbags or concrete blocks to enhance protection against anti-tank rounds and mines. An estimated 7,000 U.S. Shermans were lost in combat during , with total Allied losses higher due to distributions, though production volume ensured sustained operational availability. While the M4's sloped hull design drew conceptual parallels to the Soviet , its development predated widespread U.S. exposure to that tank, focusing instead on American industrial strengths for iterative improvements. Complementing the Sherman in armored units was the M4 mortar motor carriage, a specialized variant based on the M3 half-track chassis that mounted an 81 mm for mobile support. Standardized in late 1942 but entering production in , it allowed rapid deployment of high-explosive rounds up to 3,650 meters, filling gaps in divisional during fluid maneuvers. In the theater, the M4 provided close-range bombardment for advances, such as during the push across after , where its half-track mobility enabled it to keep pace with mechanized forces while delivering against entrenched positions. Over 600 units were produced, integrating seamlessly into armored platoons for operations.

Transportation

Automobiles and motorcycles

The is a high-performance variant of the 4 Series lineup, developed by BMW's motorsport-focused M division as a dedicated two-door and . Introduced in 2014, it succeeded the coupe and convertible versions of the previous-generation M3, separating BMW's performance (M3) from its sportier two-door models to target distinct market segments. The M4 emphasizes track-capable dynamics, featuring a lightweight carbon-fiber-reinforced plastic roof that reduces center of gravity and enhances rigidity without adding significant weight. At launch, the M4 was powered by a 3.0-liter twin-turbocharged inline-six (S55) producing 425 horsepower and 406 lb-ft of in base form, paired with either a six-speed manual or seven-speed dual-clutch automatic transmission. This setup enabled a 0-60 mph time of 3.9 seconds for the , underscoring its balance of everyday usability and supercar-level sprinting. The package, introduced shortly after, boosted output to 444 horsepower, while later iterations like the second-generation G82 model introduced in 2021, with a mid-cycle facelift in 2025, raised the base model's power to 473 horsepower and the variant to 523 horsepower, with all-wheel-drive options improving traction and reducing 0-60 times to as low as 3.4 seconds. Special-edition variants have further elevated the M4's performance credentials. The 2016 M4 GTS, a limited-run model of 700 units worldwide, incorporated water-injection technology and aerodynamic enhancements inspired by BMW's racing programs, delivering 493 horsepower and sharper handling for track enthusiasts. In 2018, the M4 CS followed as another track-oriented edition limited to 3,000 units, with 460 horsepower, carbon-ceramic brakes, and revised suspension tuning for superior cornering precision. In 2025, the G82 M4 CS was introduced as a limited-run model with 543 horsepower, restricted to around 1,700 units worldwide. The M4's racing heritage is deeply rooted in the series, where has fielded M4 GT3 and DTM variants since 2014, achieving multiple championships and influencing road-car and chassis development. By 2025, the M4 lineup had seen significant updates, including a power increase to 523 horsepower in Competition xDrive models, refreshed styling with laser-enhanced taillights, and enhanced interior technology like the BMW Curved Display. Cumulative global sales of the M4 exceeded 100,000 units by this point, with the first-generation F82 model alone accounting for 57,391 examples produced from 2014 to 2020, reflecting strong demand in markets. The model's lies in its role as a for affordable high-performance coupes, blending luxury, technology, and motorsport DNA to appeal to both street drivers and track-day regulars.

Roads and railways

The in the serves as a vital strategic route linking to southwest , functioning as an economic lifeline that has boosted development in by connecting it to major hubs like and . Construction began in 1961, with key developments such as the opening in 1966 to enable access to , while major developments such as the bypass were completed by 1981, with the full network operational between 1961 and 1996 amid various economic and political delays. The route supports high traffic volumes, with nearly 122,000 vehicles passing junction 27 daily and around 81,000 through the Brynglas Tunnels in monitored sections, underscoring its role in regional connectivity. Historical development faced significant challenges, including environmental protests in the against construction and , particularly around junctions like , which contributed to delays in expansion. In the 2010s and , the proposed M4 relief road faced significant opposition and was cancelled in 2021 over environmental and cost issues. In the , upgrades have focused on technology, with new emergency areas along sections completed and opened in April 2025 to enhance safety and traffic flow. These improvements reflect ongoing efforts to manage on this high-volume corridor, which also integrates with the European E30 highway from to . Variants of the M4 designation appear globally across multiple continents, including the M4 in as a north-south metropolitan route in the Durban area serving as a coastal connector through the and uMhlanga toward ; an M4 in linking the capital to ; and Main Road (M4) in . In , sections of the former National Highway 4 (NH-4), originally spanning to via and at about 1,235 km, were renumbered under the 2010 system, with much of it now designated as NH-48, preserving its role as a key southern corridor.) No major unbuilt interstate designated M4 exists in U.S. , though broader proposals for urban highways in the mid-20th century often faced cancellation due to community opposition. Rail designations as M4 include the M4 metro line in , , an automated subway spanning 15 km with 21 stations, connecting to the city center and extending to the San Cristoforo terminus. Development progressed in phases, with initial sections from Linate to Dateo and San Babila opening prior to the final southwestern extension inaugurated in October 2024, featuring driverless trains operating at up to 80 km/h and frequencies as low as 90 seconds. This line is projected to handle 24,000 passengers per hour per direction, reducing annual car trips by 4 million and cutting CO2 emissions by over 10,000 tons.

Science and technology

Computing and electronics

The Apple M4 is an ARM-based system on a chip (SoC) developed by Apple Inc., representing the fourth generation of its custom silicon for mobile and computing devices. Announced on May 7, 2024, it powers the seventh-generation iPad Pro, enabling advanced features like hardware-accelerated ray tracing and enhanced AI processing through its integrated components. Fabricated by TSMC on a second-generation 3 nm process node (N3E) starting in 2024, the M4 contains up to 28 billion transistors and integrates a 10-core CPU with four high-performance cores and six high-efficiency cores, alongside a 10-core GPU supporting dynamic caching and mesh shading. Its 16-core Neural Engine delivers 38 trillion operations per second (TOPS), optimized for machine learning tasks in applications like Apple Intelligence. Benchmarks indicate the M4 provides up to 1.5 times the CPU performance of the preceding M2 chip while consuming half the power, with the GPU achieving up to four times faster rendering in professional workflows compared to the M2. Subsequent variants, including the M4 Pro and M4 Max with higher core counts and expanded memory support up to 128 GB, were introduced in October 2024 for the lineup, emphasizing 5 connectivity and improved capabilities. The base M4 was also adopted in the in November 2024 and the models in March 2025, while the received M4 Max and M4 Ultra variants in 2025, broadening its application in portable and desktop computing for tasks ranging from content creation to everyday productivity. In software, the m4 macro processor serves as a versatile tool for text substitution and document generation, widely embedded in systems for automating configuration and preprocessing. Originally developed in 1977 by and at as an extension of earlier processors like M3, m4 features 21 built-in macros for string manipulation, arithmetic, and file inclusion, making it Turing-complete for complex transformations. Commonly used in publishing workflows, such as generating formatted output for Ratfor, C preprocessors, and , m4 excels in creating reusable templates for technical documentation and system scripts; for example, the syntax define(VAR', value') assigns a that expands upon , enabling conditional logic and loops via recursive definitions. Its influence extends to the GNU m4 implementation released in 1990 by Seindal, which eliminated size limits from traditional versions and became integral to Unix tools like for portable software builds.

Astronomy and physics

(M4) is a located in the constellation , situated approximately 7,200 light-years from . It was independently discovered by French astronomer on May 8, 1764, and added as the fourth entry in his of deep-sky objects, although it had been observed earlier by Philippe Loys de Chéseaux in 1745. The cluster contains an estimated 100,000 stars, primarily low-mass red dwarfs and evolved stars, and has an apparent visual magnitude of 5.6, making it visible to the under . As the closest globular cluster to the Solar System, M4 provides a valuable for studying the dynamics and evolution of ancient stellar populations, with an age of about 12.2 billion years. M4 exhibits a dense core with a characteristic barred structure formed by 11th-magnitude stars, indicative of its dynamical evolution. Observations suggest the cluster may be approaching core collapse, a process driven by two-body relaxation where energy transfer leads to gravitational contraction in the core, potentially halted by binaries or a central estimated at 800 solar masses. The cluster hosts at least 43 confirmed variable stars, including RR Lyrae types that pulsate with periods of about 0.5 days, providing insights into its morphology and distance calibration. In the 1990s, imaging resolved a of about 40,000 white dwarfs in M4, revealing their cooling sequence and confirming the cluster's role in testing models for post-main-sequence stars. Recent (JWST) observations in 2025 have further probed M4's lower down to the hydrogen-burning limit and analyzed the cooling sequence, indicating potential oxygen deficiency in low-mass stars and investigating excesses possibly from circumstellar debris. These studies enhance understanding of multiple stellar populations within the cluster, with variations in helium and light elements affecting its color-magnitude diagram. In astronomical classification, the M4 spectral subclass denotes late-type M dwarfs and early brown dwarfs exhibiting initial methane (CH₄) absorption features in their near-infrared spectra, marking the transition toward cooler objects. This subclass was formalized through spectroscopic analysis in 1996, highlighting weak CH₄ bands at 1.6–1.7 μm and 2.2 μm alongside dominant H₂O and CO absorption. Gliese 229B, the first confirmed example, displays these methane signatures, distinguishing it from earlier M types and paving the way for the T dwarf classification, with effective temperatures around 900–1,000 K. Such objects, with masses between 13 and 80 Jupiter masses, bridge stellar and planetary regimes, and their spectra inform models of dust clouds and atmospheric chemistry in substellar atmospheres.

Biology and chemistry

The M4 (M4 mAChR), encoded by the CHRM4 located on 11p11.2, is a G-protein-coupled receptor primarily expressed in the . This receptor couples to Gi/o proteins, inhibiting adenylate cyclase activity and modulating potassium channels to reduce neuronal excitability. In the brain, M4 mAChR plays key roles in cognition, including attention and memory processes, as well as pain modulation through interactions in the and . It is highly expressed in regions such as the , where it contributes to and learning, comprising a significant portion of muscarinic binding sites alongside M1 and M2 subtypes. Antagonists targeting M4 mAChR, such as tropicamide, have been utilized in since the late 1950s for inducing and during eye examinations, with U.S. approval in 1960. Tropicamide exhibits selectivity for M4 over other subtypes, blocking acetylcholine-mediated responses in ocular tissues. Research history on M4 mAChR includes knockout studies in mice from the early , which demonstrated links to models; for instance, M4 receptor-deficient mice exhibit hyperactivity, disrupted social behavior, and impaired sensorimotor gating, mimicking positive symptoms of the disorder. These findings, supported by observations of reduced M4 expression in postmortem hippocampal tissue from patients, highlight its therapeutic potential. Recent advancements include 2025 investigations into selective agonists for , emphasizing their role in enhancing signaling to improve cognitive deficits. For example, positive allosteric modulators of , often combined with activation, have shown promise in preclinical models by restoring hippocampal function and reducing amyloid-beta pathology. In , the notation M4 often refers to tetranuclear metal clusters (M4) in metal-organic frameworks (MOFs), where four metal ions form a core unit coordinated by organic ligands to create porous structures for applications like gas storage and . These M4 clusters, such as [Co4] or [Mn4] units, are typically synthesized via hydrothermal reactions involving metal salts and multidentate ligands under high-pressure aqueous conditions at 100–200°C, yielding stable frameworks with tunable pore sizes. The μ4 bridging mode in these clusters enhances structural integrity, as seen in poly[aqua-(μ4-4-carboxylatomethylbenzoato)] frameworks, facilitating efficient ligand-metal interactions.

Arts and entertainment

Music and performing arts

MarchFourth, commonly abbreviated as M4, is an American musical and performance ensemble founded in , in 2003, blending traditions with elements, , and punk influences to create high-energy live spectacles. The group features eight horn players, four drummers, electric guitars, stilt-walkers, and acrobats, drawing inspiration from New Orleans marching bands while incorporating a wide palette of styles from to . Their performances emphasize communal celebration, often encouraging audience participation through dancing and interactive street parades, and have toured extensively across the , including appearances at festivals like the . M4's discography includes several albums that showcase their eclectic sound, such as the self-titled debut (2006), Rise Up (2011) with songs like "Ninth Ward Calling" that highlight their rhythmic drive and social themes, and Rise Up (2009), featuring tracks like "" which gained wider recognition as the closing credits theme for the 2013 Pixar film . Later releases, including Magic Number (2016) recorded in New Orleans with producer Ben Ellman and guests like , the EP Worth It (2023), and the self-titled album (2024), continue to evolve their brass-heavy, horn-forward style, receiving praise for their cinematic energy and community-driven ethos. Audience reception has been enthusiastic, with live shows noted for their visual and sonic immersion, fostering a sense of uninhibited joy. In musical instruments, the Seagull M4, introduced in 2017 by the Canadian luthier Seagull Guitars, is a compact, portable 4-string diatonic acoustic instrument inspired by the Appalachian dulcimer, designed to simplify melody-making for beginners while offering a bright, twangy tone tuned to D-A-D. Crafted in La Patrie, Quebec, with options in spruce or mahogany tops and an optional EQ for amplified play, the M4 features a guitar-like neck for easier fretting than traditional dulcimers, making it suitable for folk, strumming, and casual performances. Its diatonic scale limits complexity but enables quick learning of simple tunes, positioning it as an accessible entry point into stringed folk music. Post-2000 releases titled M4 include the 2006 EP by Canadian Faunts, classified in the and genres, which explores atmospheric soundscapes through synth-driven tracks. In experimental , Autechre's track "M4 Lema" from the 2020 album exemplifies abstract compositions with intricate, algorithmic rhythms and elements, contributing to the duo's influential body of work in avant-garde . Additionally, M4 Vaporwave, an artist from active since around 2016, produces and tracks that manipulate retro samples into lo-fi, nostalgic sound collages, gaining a niche following in underground scenes.

Film, television, and literature

The , adopted by the U.S. military in 1994 following lessons from the 1991 , began appearing in film and television depictions of contemporary conflicts in the late 1990s, symbolizing modern infantry versatility and close-quarters effectiveness. Its shortened barrel and lighter weight made it a staple prop in action sequences, often highlighting themes of and . In cinema, the M4 gained prominence in Black Hawk Down (2001), where it is anachronistically wielded by U.S. Army Rangers and Delta Force soldiers during the recreated 1993 Battle of Mogadishu (though not yet in service at the time), contributing to the film's portrayal of military tactics. The weapon recurs in Transformers (2007), equipped by U.S. soldiers combating alien invaders, reinforcing its status as a standard-issue rifle in blockbuster military sci-fi. Other notable films include Lone Survivor (2013), depicting Navy SEALs using customized M4 variants in Afghan mountains, which amplified public awareness of the carbine's adaptability in real operations. Television series have similarly integrated the M4 to depict counter-terrorism and survival narratives. In 24 (2001–2010), CTU agents and military personnel carry M4 carbines in rapid-response scenarios, emphasizing its quick deployment in high-tension plots. The weapon appears in The Unit (2006–2009), portraying Delta Force missions with authentic loadouts, including suppressors and optics, to convey operational precision. More recently, The Terminal List (2022) on Prime Video features the M4 in vigilante sequences inspired by Navy SEAL experiences, blending thriller elements with tactical realism. In video games, the has been a cornerstone of first-person shooters, particularly the series starting with Call of Duty 4: Modern Warfare (2007), where it is modeled as the M4A1 assault rifle used by and USMC forces. Players unlock it early in the campaign via default loadouts or multiplayer progression, with stats including a 30-round , 800 rounds-per-minute fire rate, and compatibility with attachments like the ACOG scope or for enhanced versatility. Subsequent entries, such as Call of Duty: Modern Warfare (2019), allow extensive customization of the M4A1—including barrels, stocks, and underbarrel grips—making it a meta-favorite for its balanced damage (30-40 per shot at range) and low recoil, influencing and community mods. The series' accurate depictions, drawn from real military specs, have cemented the M4's cultural icon status among gamers, with over 500 million copies sold (as of 2023) featuring the weapon. Literature featuring the M4 is primarily , such as detailed histories in by McNab (2021), which analyzes its design evolution and combat history without fictional elements. In military thrillers, it receives minor references as standard gear, as in Jack Carr's series, where protagonists employ it in realistic scenarios.

Other uses

Sports and recreation

In , a recreational simulating tactical with non-lethal 6mm projectiles, the replica serves as one of the most widely used platforms due to its and ergonomic handling. These replicas, powered primarily by battery-operated mechanisms, replicate the form and semi-automatic or full-automatic firing modes of military-style while adhering to safety limits, typically capping at 350-400 feet per second () with 0.20g s to minimize . Popular variants include Automatic Electric Gun () models such as the VFC VR16 series, praised for its full-metal construction and programmable electronic trigger response, and the Umarex HK416 A5 by VFC, which offers enhanced durability through licensed trademarks and quick-change spring systems for field-adjustable power levels. Airsoft M4 usage is regulated by a combination of venue-specific guidelines and national laws to promote safe play, requiring participants to wear full-face protection meeting ANSI Z87.1 standards, maintain a minimum engagement distance of 10-50 feet depending on power output, and cover barrels with tips when not in active games. , federal regulations under the Imitation Firearms Act mandate a permanent 6mm-wide blaze marking on all imported or transported guns to distinguish them from real firearms, with violations punishable by fines. standards saw significant updates in the 2020s, including the Product Safety Commission's (CPSC) 2023 rule extending the Imitation Firearms Act to non-powder-actuated imitation firearms like replicas, requiring third-party certification for permanent marking compliance, effective June 26, 2023, with a transition period until January 1, 2024. Competitive airsoft events featuring M4 replicas emerged prominently in the as the expanded beyond casual skirmishes into organized tournaments, with early milestones including the growth of scenario-based games in and that emphasized tactics and objective capture. Tournaments such as those under the International Airsoft Alliance or field-hosted events often categorize M4 AEGs in standard rifle divisions, where players compete in formats like or woodsball, highlighting the weapon's balance of accuracy and up to 20 rounds per second. Global participation has grown substantially, with the airsoft guns market—dominated by M4-style rifles—valued at USD 2.1 billion in and projected to reach USD 4.8 billion by 2034, driven by rising interest in recreational among a growing global community of enthusiasts, particularly in events drawing thousands per competition. In , M4 designations appear in components like the Clarks M4 hydraulic system, a option for riders featuring a four-piston caliper design that provides powerful braking for enduro, downhill, and electric mountain bikes on varied terrain. This system, compatible with standard 160-180mm rotors, uses for low-maintenance operation and integrates with 4-speed or higher drivetrains common in mountain bikes, providing reliable without the complexity of higher-end servo-assisted models.

Miscellaneous

In , M4 historically denoted a broad measure of the United Kingdom's , encompassing sterling notes and coins, household and private non-financial corporation deposits, and short-term securities such as and bonds with maturities up to five years. This aggregate was tracked by the from 1982 until its discontinuation in 2016, after which focus shifted to other monetary indicators. The M4 postcode district is located in Manchester, England, primarily covering the neighborhoods of Ancoats, the Northern Quarter, and Strangeways, serving as an administrative area for postal addressing in this urban region. These postcodes facilitate mail distribution in central Manchester's mixed residential, commercial, and industrial zones. In business contexts, M4 refers to official forms and programs, such as Minnesota's Corporation Franchise Tax Return (Form M4), which unitary businesses use to report income and file combined returns including domestic corporations and certain insurance entities. Similarly, Maryland's Manufacturing 4.0 (M4) Program provides grants covering up to 50% of costs for manufacturers adopting Industry 4.0 technologies like automation and data analytics, with awards ranging from a minimum of $25,000 to a maximum of $500,000 per project.