Product DescriptionThe FAXON FIREARMS ARAK-21 complete upper receiver is a gas piston actuated upper assembly built to interface with standard AR-15 lower receivers using only the takedown and pivot pins. Designed for fast installation with no tools, this 5.56 NATO upper delivers a distinctive long-stroke piston operating system, a one-piece 6061-T6 aluminum billet receiver, and a configurable rail layout for optics and accessories. The included Barrel Assembly Unit combines the barrel, gas block, muzzle brake, gas piston, gas adjuster, and barrel trunnion into a streamlined system, while the 4-position gas adjuster allows the shooter to tune gas flow for optimal operation or single shot use. With its ambidextrous, non-reciprocating charging handle and full-length Picatinny top rail, the ARAK-21 is engineered for versatility, durability, and modern AR-platform performance.Product Highlights Complete ARAK-21 upper receiver assembly chambered in 5.56 NATO for compatibility with standard AR-15 lower receivers Long-stroke gas piston system with 4 gas settings, including a no-gas setting for single shot operation One-piece 6061-T6 aircraft-grade aluminum billet receiver with full-length top Picatinny rail and additional accessory rails 12.5 inch configuration with integrated Barrel Assembly Unit for simplified maintenance and rapid system changes Includes essential components and tools such as the bolt carrier assembly, recoil system, manual, and BAU removal tools Specs Brand: FAXON FIREARMS Model: ARAK-21 Product Type: Complete Upper Receiver Caliber: 5.56 NATO Barrel Length: 12.5 inches Color: Black Material: 6061-T6 aluminum billet Gas System: Long-stroke gas piston Gas Adjuster: 4 settings Charging Handle: Ambidextrous, non-reciprocating, foldable, spring returned Rail Configuration: Full-length top Picatinny rail with additional aluminum Picatinny rails Compatibility: Standard AR-15 lower receivers via takedown pin and pivot pin Included Components: ARAK-21 upper, Barrel Assembly Unit, charging block, standard charging handle, lower forearm with screws, three aluminum full-length Picatinny rails, three insulating shims, bolt carrier assembly, lower recoil lug with spring guide rod, dual recoil spring system, owner&';s manual, two Allen wrenches, shipping box, BAU removal tools, magazine marker bands, bolt(s) and firing pin(s) for ordered calibers, recoil spring(s) for ordered calibers Approximate Weight: 5 lb UPC: 816341025608 MPN: URSSB556P Disclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product&';s manufacturer.