Complete Bolt Carrier Group designed to operate with AR-15 platform firearms chambered in 6.5 Grendel, 6mm ARC, or 22 ARC. Bolt (Type II): 9310 steel with phosphate finish; Carrier: 8620 steel, chrome lined, phosphate finish; Extractor: 4140 steel, phosphate finish. All CMMG products come with Lifetime Quality Guarantee.