UltiMAK M13 Optic Mount Picatinny / Weaver Rail One-piece aluminum optic mount clamps rock-solid to barrel. This is the lightest, lowest, best mount available. One-piece aluminum mount body (6061-T6). Hard anodized. Barrel clamps are 4140 steel, secured with alloy steel cap screws. Easy installation instructions included. Made in U.S.A. Based on the M1-B and M2-B, but with shorter overall Length - 4.625" (4 & 5/8")