Cryptic Bolt Assembly - Complete .308 WIN/7.62x51mm Nickel Boron. HPT (High Pressure Batch Tested) and MPI (Magnetic Particle Inspected). Comes Assembled. Specifications for Cryptic .308 WIN/7.62x51mm Bolt Assembly - Complete: Manufacturer: Cryptic Fabric/Material: 4140 Billet Tool Steel Carpenter 158 Steel Carrier Material: 8620 Steel Bolt Material: Steel Caliber: 7.62x51mm NATO .308 Winchester Gun Make: AR Platform Gun Model: AR-10 Hand: Ambidextrous Weight: 2 oz Condition: New Included Accessories: Standard Package Contents: Cryptic .308 WIN/7.62x51mm Bolt Assembly - Complete Bolt Tool Steel Extractor Assembly (spring with viton insert pin extractor) Ejector Assembly (ejector spring roll pin) Gas Rings - Set of 3 What firearm models does the manufacturer say Cryptic .308 WIN/7.62x51mm Bolt Assembly - Complete is compatible with? The manufacturer says that Cryptic .308 WIN/7.62x51mm Bolt Assembly - Complete is compatible with AR-10Cryptic CC-BAC-0205: Bolt Assembly - Complete .308 WIN/7.62x51mm Nickel Boron