Bolt Assembly  Bolt: Shot Peened Magnetic Particle Inspected and Marked Bolt Material:  9310 Alloy Steel Compatibility: .223 / .556 / 300BLK Extractor: Shot Peened Hardened tool Steel Extractor 0-Ring: Viton, Mil-Spec Gas Rings (3): Mil-Spec Finish: NICKEL BORON Bolt Carrier  Material: 8620 Steel Design: Heavy Profile M16 Style (Preferred for most AR-15 Builds) Gas Key Screws: Grade 8 Properly Torqued and Staked to Mil-Spec Finish: NICKEL BORON Cam Pin:  Material: 4140 Steel Finish: NICKEL BORON Firing Pin Material: 8740 Steel Centerless ground Hard Chrome Plated Weight: 11.6 Ounces   100% USA Made