RISE Armament advanced M16 Bolt Carrier Group (BCG) with Nickel Boron finish is manufactured with precision and individually inspected to ensure high-level performance. Coated with nickel boron to reduce friction and improve overall performance. Coated with nickel boron to reduce friction and improve the rifle's overall performance Unit weight: 11.6 oz. Individually MPI tested Bolt: 9310 MPI tested Carrier: 8620 tool steel heat treated and case hardened Gas key: tool steel - grade 8 hardened fasteners and staked properly Cam pin: 4140 steel Extractor: tool steel - shot peened