FailZero AR10, Bolt Carrier Group, Black, No Hammer FZ-AR10-NH-BLACK This AR10 Black Bolt Carrier Group (BCG) comes fully assembled and ready to drop into most Spec AR10 upper receivers. All critical parts are coated with EXO Nickel Boron Technology that provides permanent dry lubricity" extreme durability and increases both wear and corrosion resistance. Black topcoat on the carrier only.