Bolt Carrier Group Assy. 5.56 NATO M16 Profile Nitride Bolt & Carrier Retail Packaged – The 223 Bolt and Bolt Carrier group comes complete with Cam Pin Firing Pin and Firing Pin Retainer. – Compatible with 5.56 NATO .223 REM and .300 Blackout – RF-85 Treated: Non-treated – Bolt Carrier Finish: Nitride – Bolt Carrier Material: 8620 Steel – Bolt Finish: Magnesium Phosphate – Bolt Material: 9310 Steel