Guntec USA AR .308 Cal Bolt Carrier Group BCG MIL-SPEC Rainbow. The goal is to distribute excellent quality at an economical value. Specifications for Guntec USA AR .308 Cal Bolt Carrier Group (BCG) MIL-SPEC: Manufacturer: Guntec USA Finish: Matte PVD Fabric/Material: 17-4 Stainless Steel Bolt Material: 9310 Steel Caliber: 7.62x51mm NATO .308 Winchester Hand: Right Weight: 18 oz Features of Guntec USA AR .308 Cal Bolt Carrier Group BCG MIL-SPEC Made for 7.62X51/308 cal. Hardened extractor S7 tool steel. The group comes fully assembled with properly torqued and staked gas key. HPT/MPI Tested and marked. 8620 Carrier and Gas Key. Package Contents: Guntec USA AR .308 Cal Bolt Carrier Group MIL-SPEC Guntec USA GT-BCG-308-RPVD: AR .308 Cal Bolt Carrier Group MIL-SPEC Rainbow