This high quality bolt carrier group is a valuable addition to your AR15 build. 11.52 oz. 5.56 CHROME LINED PHOSPHATE BCG: Available with or without "A" Logo 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 5.56 NICKEL BORON BCG No Aero 'A' Logo Machined from 8620 Tool Steel (Carrier) and 9310 Steel (Bolt) Carrier h Mfg: Aero Precision