This bolt carrier is a valuable addition to your AR-15 build. It features a properly staked gas key, forward assist serrations, a black O-ring insert on the extractor, and is made of steel. M16-cut carrier, Machined from 8620 Tool Steel (Carrier) and 9310 Steel (Bolt), Carrier has forward assist serrations, Black Nitride Finish - advanced lower friction coating that minimizes the need for lubricants and cleaning, Properly staked gas key, Shot peened, HPT tested/MPI marked, Black o-ring insert on extractor, High quality BCG