Cryptic AR15 Bolt Carrier Group Dragon's Breath. Bolt carrier 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 AR15 Bolt Carrier Group: Manufacturer: Cryptic Color: Dragon's Breath Finish: Chrome Fabric/Material: 8620 Aircraft Quality Steel Gun Make: AR Platform Gun Model: M16 M4 AR-15 Features of Cryptic AR15 Bolt Carrier Group Coefficient of Friction 0.2 Hardness 3200 Vickers Max Temperature 750 degrees F Thickness 2-3 microns Reduced Carbon Fouling Easier Cleaning Key Staked with Grade 8 Screws per Mil-Spec Full Auto Carrier (Backward compatible with all semi-auto rifles) Package Contents: Cryptic AR15 Bolt Carrier Group What firearm models does the manufacturer say Cryptic AR15 Bolt Carrier Group is compatible with? The manufacturer says that Cryptic AR15 Bolt Carrier Group is compatible with AR-15 M4 M16Cryptic CC-BCK-0110: AR15 Bolt Carrier Group Dragon's Breath