The FailZero® AR-15 .458 SOCOM Nickel Boron Bolt Carrier Group (BCG) comes fully assembled and ready to drop into most mil spec .458 SOCOM Upper Receivers. All critical parts are coated with EXO Nickel Boron technology that provides permanent dry lubricity” extreme durability” and increased wear and corrosion resistance. The patented Nickel Boron coating will reduce friction and improve the overall performance of your rifle.