This Colt AR-15 Bolt Carrier includes a complete mil-spec bolt assembly with bolt carrier, firing pin, and properly staked gas key (carrier and gas key are chrome lined). The Colt Bolt Carrier Assembly will allow you to be prepared to face intensive tactical operations with the confidence of knowing your weapon won't let you down. These parts are precision engineered and manufactured to strict quality control standards from the finest materials for correct fit in your gun. The supply of these AR-15 bolt carrier groups is very limited, so make sure to pick one up for your next rifle build or for use as a spare before it's too late!