DPMS Toolcraft 5.56x45mm NATO/.300 AAC Blackout Bolt Carrier Group Chrome Lined Phosphate. Gas key is machined out of bar stock chrome lined phosphate coated and secured with grade 8 fasteners and staked per mil-spec. Bolt carrier is phosphated outside and chrome lined inside. For packaging considerations BCG will be packed dry. As a result it will have a grey dusty appearance that will turn black with the application of CLP or other preferred lubricant. Specifications for DPMS Toolcraft 5.56x45mm NATO/.300 AAC Blackout Bolt Carrier Group: Manufacturer: DPMS Finish: Chrome Lined Phosphate Caliber: 5.56x45mm NATO .300 AAC Blackout Package Contents: DPMS Toolcraft 5.56x45mm NATO/.300 AAC Blackout Bolt Carrier Group DPMS DP51655109766: Toolcraft 5.56x45mm NATO/.300 AAC Blackout Bolt Carrier Group Chrome Lined Phosphate