The Manticore Arms Transformer Rail comes with the rail, barrel nut, polymer grip panels, (3) M-LOK panels, mounting screws, required allen wrenches, and instruction sheet. The barrel nut is easily mounted using an M4 castle nut wrench. FeaturesAR-15 Aluminum Free Float rail system with ability to intermix Keymod, M-LOK, and polymer grip panelsDimensions: 15" length, 1.5" exterior width, 1.09" interior clear widthWeight: 8.4 ounces for rail, 1.5 ounces for barrel nut, under 0.3 ounces per panelWeight installed: 9.9 ounces (only adds 7.4 ounces as original barrel nut is removed)Barrel nut material and finish: 6061 6061 T6 aluminum with Milspec Type III Black hardcoat anodizingRail material and finish: 6061 T6 aluminum with Milspec Type III Black hardcoat anodizingPanel material and finish: 6061 black anodized aluminum and proprietary polymerSix Transformer panel mounting locationsGEN II barrel nut design is lighter, simpler, and easier to install! Just torque to the recommend barrel ...