The FailZero LR-308 Bolt Carrier Group comes fully assembled and ready to drop into most properly chambered Mil-Spec upper receivers. The extractor hardware includes a heavy spring, silicone insert, and o-ring to give better extraction tension.Nickel Boron BCGs feature critical parts that are coated with EXO Nickel Boron technology that provides permanent dry lubricity, extreme durability and increases both wear and corrosion resistance. EXO Nickel Boron makes for easy cleanup and will improve the performance of your rifle.The Black carrier comes with a black topcoat/exterior with FailZero EXO Nickel Boron underneath. FailZero introduced this carrier to provide non-reflective properties, resulting in a Tactical Advantage. However, PLEASE NOTE that wear areas including ramps, rails, and other contact points such as carrier ends will wear - exposing the Nickel Boron coating beneath. The critical non-wear areas which are exposed during operation, i.e. the dust cover area will remain bl...