M16 Style Carrier Machined from 8620 Steel Heat Treated Final Grind Before Plating Polished Nickel Boron Coating (NiB-X) 5.56/.223 Bolt Machined from 9310 Steel Heat Treated Shot Peened MPI Polished Nickel Boron Coating (NiB-X) Billet Gas Key Machined from Solid Billet of 4140 Steel Properly Seated with Grade 8 Fasteners Properly Staked Polished Nickel Boron Coating (NiB-X) Cam Pin Machined from 4140 Steel Heat Treated and Ground Polished Nickel Boron Coating (NiB-X) Billet Extractor Machined from Solid Billet of 4140 Steel Phosphate Coated Extractor Insert Included Viton O-Ring Included Firing Pin Machined from 8640 Steel Hard Chrome Plated 100% American Made