This Black Dawn "Multi Function Rail" is CNC machined from 6061 Aluminum then Hardcoat anodized to Mil-Spec 8625 req. then Laser Etched with "T-Markings". Comes complete with Barrel Nut anti rotation screws and End Cap. The "MFR" rail comes in a "Mid Length" size, and will function with carbine length gas systems with use of a Low Profile gas block, this rail also works with the Osprey Defense Ops 416 Gas Piston System.