This Battle Arms Development Standard Bolt Carrier Group is Black Nitride finished with an ultra-hard, corrosion resistant top surface layer for wear resistance and minimal need for lubricants. Machined from the very best materials for reliable use and longevity. The laser engraved BAD Inc logo let's you know this BCG isn't standard, it sets the standard. Features Bolt Carrier: 8620 Steel Case Hardened, Machined from BilletFiring Pin: 8740 Steel, Center-less Ground, Hard ChromedGas Key: 4130 Steel with Grade 8 Screws, Properly Staked, Machined from BilletCam Pin: 4340 Hardened SteelBolt: 9310 Steel, Cased Hardened, Shot Peened, Mil-Spec Dimensions, CNC Ground After Heat TreatExtractor: 4340 Steel, Manganese Phosphate Finished for Positive Grip