Complete, mil-spec assembly with bolt, bolt carrier, and firing pin ready to drop into the rifle or carbine upper of your choice. Each bolt assembly is high pressure tested and 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. M16-style carrier on the black phosphate model has full-length shroud for tripping auto sear, so this carrier may be installed on full-auto law enforcement and military rifles. Carrier and gas key are chrome lined for smooth cycling and resistance to wear from hot combustion gases for years of dependable service.