Rail section is made of Hard Anodized Aircraft Aluminum Alloy. Mounting hardware is made of Corrosion Resistant Stainless Steel Made to the Mil-Standard 1913 Picatinny Arsenal Specifications. Available in three Lengths: 3-inch (5 slot), 4-inch (7 slot) and 5.5-inch (11 slot) Features a Snag resistant design, while retaining Mil-Standards specs. Self-contained assembly, eliminates the possible loss of mounting hardware. Fits ALL KeyMod(TM) interface mounting surfaces.Installation Instructions:a Locate the forward position of the mount, indicated by the arrow marking on the bottom of the rail section, ensure the arrow points towards the muzzlea With a T15 Torx(TM) wrench, loosen (counter-clockwise) the mounting screws enough to allow the anchoring nuts to drop in and slide fully forward into the desired mounting position of your KeyMod rail systema Tighten screws (clockwise) until firmly secured (DO NOT exceed 18-20 in-lbs)a For more secured mounting, apply blue thread locking compound to screw threads only.