Cryptic AR10 Steel Bolt Carrier Mystic Black. 308 WIN / 7.62x51mm / 6.5 Creedmoor) machined from Mil-Spec 8620 aircraft quality steel with shrouded firing pin and Mil-Spec chrome lined interior. BCG includes the proper chrome lined and heat treated gas key. Gas key is secured to carrier with Grade 8 fasteners and properly staked per Mil-Specs. This ensures a strong staking and proper gas system functioning. Specifications for Cryptic Steel Bolt Carrier: Manufacturer: Cryptic Fabric/Material: Steel Gun Make: AR Platform Condition: New Features of Cryptic Steel Bolt Carrier Compatible w/ any DPMS LR308 platforms Mil-Spec Bolt Carrier Machined from 8620 Aircraft Quality Steel and heat treated to 60-61 RC Mil-Spec Chrome Lined Carrier Interior Mil-Spec Chrome Lined Gas Key Key Staked with Grade 8 Screws per Mil-Spec Full Auto Carrier (Backward compatible with all semi-auto rifles) Package Contents: Cryptic Steel Bolt Carrier What firearm models does the manufacturer say Cryptic Steel Bolt Carrier is compatible with? The manufacturer suggests that Cryptic Steel Bolt Carrier is compatible with AR-10 AR-15Cryptic CC-BCK-0200: AR10 Steel Bolt Carrier Mystic Black