Lockstep Arms Billet MOS Optic Plate Cover Black. Fill the gap with the Lockstep Arms Optic Billet Plate Cover. Specifications for Lockstep Arms Billet MOS Optic Plate Cover: Manufacturer: Lockstep Arms Color: Black Fabric/Material: CNC Machined Quantity: 1 Finish: Anodized Features of Lockstep Arms Billet MOS Optic Plate Cover Compatible With Any MOS Cut Slide. CNC Machined for Precision Fitment Package Contents: Lockstep Arms Billet MOS Optic Plate Cover Lockstep Arms LA-GLK-1200-BLK: Billet MOS Optic Plate Cover Black