This Full Top Rail model means that the Picatinny top runs from beginning to end. This gives tons of room for any accessories you may want to mount on top. 15 Full Top Rail MLOK Handguard (Includes Barrel Nut & Hardware). Handguard is made of 6061-T6 aluminum and anodized black per mil-spec MIL-A-8625F, TYPE III, CLASS 2. The barrel nut is 4140 PH steel. Full top rail + MLOK slots on 7 other sides. Includes anti-rotation tabs. Hand guard weighs 10.0 ounces. Barrel nut and hardware weigh an additional 2.6 ounces.