AIM AR/M16 .223/5.56 complete Bolt Carrier Groups. We are having these bolts manufactured to our exacting standards with no Frills added to be able to offer the best BCG at the Best Price! Features 9310 Bolt Material; 8620 Chrome lined carrier and gas key; Properly staked Investment cast gas key hardened to USGI specifications fastened with Hardened Grade 8 Fasteners; Shot peened MPI (Magnetic Particle Inspected) Bolt. Extractor includes Black Insert. This is an Excellent Bolt and an Excellent Price!