The heart of a reliable AR-15 build is a quality 5.56 bolt carrier group assembly. These are the same high quality BCG's we make for law enforcement and military groups around the world. Machined to mil-spec dimensions and finished in a beautiful black nitride finish, this bolt will continue to run and looks great doing so. Specifications: Machined from 8620 alloy steel with a QPQ black nitride finish 5.56 Bolt is machined from Carpenter 158 tool steel High pressure tested (HPT) and magnetic particle inspected (MPI) Shot peened M16-cut/full auto capable carrier Properly staked gas key secured to the carrier with grade 8 fasteners Carrier has forward assist serrations