UltiMAK M2-B Picatinny Optic Mount (with Vent Holes) Picatinny/Weaver style rail WITH VENT HOLES. Clamps directly to barrel for rock-solid stability and accuracy. Solid, one-piece 6061-T6 hard anodized aluminum body. Comes with 4140 steel clamps, screws, allen wrench, and instructions. No gunsmithing. Made in USA