DLC exterior coated to Noveske specification with chrome lined bore. Machined to USGI specifications. Carrier is made out of Aircraft grade, domestically sourced proprietary 8620 steel. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestically manufactured Grade 8 fasteners and properly staked per Mil-Spec.