The Cry Havoc Tactical QRB (Quick Release Barrel) 2 Pin Upper Receiver Takedown Kit for AR-15 style rifles or pistols. While the QRB was primarily designed for the civilian market, non-civilian applications range from the Air Force using the QRB on the Air Crew Survival Weapon (GAU-5A) for ALL Fighters and Bombers, Motorcycle Police who did not have room for a standard AR-15/M4, to Operators in areas where an exposed AR-15/M4 might bring unwanted attention. In these and other cases, where there is a need for an AR-15/M4, the QRB now makes it possible to fit a rifle into a tight space but still have a usable barrel length for increased velocity. Assemble and Fire in seconds, even i Mfg: Brownells