The FailZero AR-15 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 Nitride BCG is designed for shooters looking for a tactical advantage resulting from the non-reflective properties of Black Nitride. The carrier comes with a Black Nitride finish for great corrosion protection and wear resistance. All critical parts are Black Salt Bath Nitride Finished which provides durability and increases both wear and corrosion resistance, while the firing pin has a chrome finish.The Black carrier comes with a black topcoat/exterior ...