This Black Dawn "Multi Function Rail" is CNC machined from 6061 Aluminum, Hardcoat anodized to Mil-Spec 8625 requirements and Laser Etched with "T-Markings". This rail system comes complete with Barrel Nut anti rotation screws and End Cap. The "MFR-C" rail comes in a "Carbine" size, and will function with carbine length gas systems, this rail also works with the OSPREY DEFENSE Ops 416 Gas Piston System.