B5 Systems End Plate Steel Black. The limited rotation one piece steel construction allows for proper staking and a lifetime of service. The commercial manganese phosphate finish is corrosion resistant. Specifications for B5 Systems End Plate Steel: Manufacturer: B5 Systems Color: Black Fabric/Material: Steel Gun Model: M16 M4 AR-15 Country of Origin: USA Limited Rotation Phosphate Finish Steel Construction Compatible with all MIL-SPEC Receiver Extensions Package Contents: B5 Systems End Plate Steel What firearm models does the manufacturer say B5 Systems End Plate Steel is compatible with? The manufacturer says that B5 Systems End Plate Steel is compatible with AR-15 M4 M16B5 Systems AEP-1090: End Plate Steel Black