Complete, mil-spec assembly with bolt, bolt carrier, and firing pin ready to drop into the rifle or carbine upper of your choice. .223/5.56 fits standard AR-15/M16/M4 rifles. Each assembly is magnetic particle inspection tested to ensure it’s free from imperfections that can lead to premature failures. Properly staked gas key prevents gas leakage that can lead to short stroking. Black Nitride finish. UM Tactical Skull Logo laser-engraved
Proudly made in the USA.