VDI direct impingement full auto rated bolt carriers are compatible with mil-spec and non mil-sped upper receivers and associated components. This bolt carrier is machined to meet all MIL TDP specifications. The complete Bolt Carrier Group comes with: VDI LifeCoat Bolt Carrier VDI 5.56 Bolt Assembly VDI Firing Pin VDI Cam Pin Cotter Pin The new Integral D.I. Carrier was designed from conception to improve the service life and durability of the direct impingement carrier. The VDI Integral DI Carrier eliminates the potential for carrier to key separation due to carrier key screws stripping, fracturing, or becoming un-staked. The new In Mfg: Voodoo Innovations SPECS: Carrier made of 8620 Steel, Milspec Bolt C158.