Fostech AR-15 Complete Bolt Carrier Group BCG Nickel Boron FT-BCG-NB. This is a standard full-auto M16 cut Nickel Boron Bolt Carrier Group BCG. It is designed to function with the Echo AR-II and the Echo Sport. Specifications for Fostech AR-15 Complete Bolt Carrier Group (BCG): Manufacturer: Fostech Carrier Material: 8620 Steel Bolt Material: 9310 Steel Gun Make: AR Platform Gun Model: AR-15 Condition: New Package Contents: Fostech AR-15 Complete Bolt Carrier Group What firearm models does the manufacturer say Fostech AR-15 Complete Bolt Carrier Group (BCG) is compatible with? The manufacturer says that Fostech AR-15 Complete Bolt Carrier Group (BCG) is compatible with AR-15Fostech FT-BCG-NB: AR-15 Complete Bolt Carrier Group Nickel Boron