Cryptic Bolt Assembly - Complete .223/5.56/.300 AAC Blackout Mystic Silver. HPT (High Pressure Batch Tested) and MPI (Magnetic Particle Inspected). Comes Assembled. Specifications for Cryptic .223/5.56/.300 AAC Blackout Bolt Assembly - Complete: Manufacturer: Cryptic Fabric/Material: 4140 Billet Tool Steel Carpenter 158 Steel Carrier Material: 8620 Steel Bolt Material: Steel Caliber: .300 AAC Blackout 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: AR-15 Hand: Ambidextrous Weight: 2 oz Included Accessories: Standard Package Contents: Cryptic .223/5.56/.300 AAC Blackout 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 .223/5.56/.300 AAC Blackout Bolt Assembly - Complete is compatible with? The manufacturer says that Cryptic .223/5.56/.300 AAC Blackout Bolt Assembly - Complete is compatible with AR-15Cryptic CC-BAC-0103: Bolt Assembly - Complete .223/5.56/.300 AAC Blackout Mystic Silver