RISE Armament Nickel Boron Bolt Carrier Group is a perfect start to any custom AR-build, or as a solid upgrade to an existing rifle. It features a Nickel boron coating, a columnar-formed compound composed of about 95 percent nickel and 5 percent boron. This formation reduces the contact points between surfaces while simultaneously providing an additional level of hardness to the steel. The result is a natural lubricity and improved durability. When compared to the industry standard chrome coating, the nickel boron coating offers greater resistance to corrosion for a significantly longer service life. Features: Unit weight: 11.6 oz. Individually MPI testedBolt: 9310 MPI testedCarrier: 8620 tool steel heat treated and case hardenedGas key: tool steel - grade 8 hardened fasteners and staked properlyCam pin: 4140 steelExtractor: tool steel – shot peened RISE Armament RA-1011 AR-15 .223/5.56 Nickel Boron Bolt Carrier Group RA-1011-SLVR