Failzero Bolt Carrier GroupM16/4 Full Auto BCG- No HammerA completely assembled, ready to install Full-Auto BCG with no hammerFully assembled ready to drop into most mil spec M16, M4 or AR15 upper receiversAll critical parts are coated with EXO Nickel Boron technology that provides permanent dry lubricity, extreme durability and increases both wear and corrosion resistancePatented Nickel Boron coating will reduce friction and improve overall performance of rifleNickel Boron treated parts include:Bolt & Extractor (5.56/.223 compatible)Bolt CarrierExtractorCam PinCarrier KeyFiring Pin