The Faxon ARAK-21 XRS is a unique hybrid upper receiver that combines AR-15 ergonomics with an AK-style long-stroke piston system. It mounts to a standard AR-15 lower receiver, giving the shooter AR familiarity while providing the reliability benefits of a piston-driven AK-style action. Type: Semi-Auto Rifle Action: Long Stroke Piston Caliber: 5.56x45mm Capacity: 30 Year introduced: 2015, USA Weight: 7.5 oz Overall length: 32" Status: Active Intended use: Range, Home Defense, Military Surplus Users