The Geissele 5.56mm Reliability Enhanced Bolt Carrier Group 05-2993 is a full-mass, full-auto rated M16/M4 bolt carrier group designed for superior performance and reliability. Manufactured in Geissele's state-of-the-art facility, this carrier group features a properly torqued and staked, chrome-lined, nano-coated gas key. The extended upper rails provide greater stability and dramatically increase feeding reliability. Coated with Nanoweapon technology, the carrier offers unmatched corrosion and wear resistance. Geissele Automatics Geissele 5.56mm Reliability Enhanced Bolt Carrier Group 05-2993