For a smoother shot at a reasonable price choose a Bootleg Inc Adjustable Carrier to modify your firearm. These Bolt Carrier Groups from the fine people at Bootleg Inc is full auto rated for strength and to prevent erosion. With a 4 setting adjustable vent system the Bootleg Inc Four Position Carrier prevents excessive gas pressure from causing a blowback. Whether you're a connoisseur or a novice a Bootleg Inc Complete Bolt Carrier Group BCG is perfect for those who need to adjust on the go. Specifications for Bootleg Inc AR-15 Four Position Adjustable Carrier: Manufacturer: Bootleg Inc Color: Black Finish: Lithium Isonite Fabric/Material: S7 Tool Steel Cartridge: 5.56mm, .223 Remington Gun Make: AR Platform Gun Model: AR-15 Condition: New Weight: 10.8 oz Bolt Material: Steel Carrier Material: S7 Tool Steel Features of Bootleg Inc AR-15 Four Position Adjustable Carrier: Machined from S7 Tool Steel 4 Setting Adjustable Vent System Gas Adjustment Full Auto Rated Staked MIL-SPEC Gas Key Removable Adjustment Pin Package Contents: Bootleg Inc AR-15 Four Position Adjustable Carrier