This all-new Bolt Carrier Group features the innovative SP4 coating—a hybrid DLC-style coating that improves wear resistance, reduces friction, and makes cleaning a breeze. SP4 is micro-porous, meaning carbon and other gunk doesn't stick like glue. That means you could throw it in the dishwasher (assuming you can convince your wife that it's a good idea) and it'll come out spick-and-span. SP4 has been tested to -44°F in Alaska and in the desert heat of the Middle East with NO lubrication—and performed flawlessly. Includes a hand polished bolt carrier with a chrome lined bore and staked gas key, bolt with gas rings, firing pin, cam pin, and firing pin retaining pin.