This high quality bolt carrier group is a valuable addition to your AR15 build. Features: M16-cut carrier Machined from 8620 steel Carrier has forward assist serrations Mil-Spec phosphate coating Properly staked gas key Chrome lined gas key and bolt channel 5.56 Bolt is machined from Carpenter 158 tool steel Shot peened HPT tested/MPI marked Black o-ring insert on extractor High quality BCG