This Primary Arms basic scope mount works with M4, AR-15, and similar "flat-top" 1913 Picatinny mounting platforms. Fits scopes with 30mm tubes, or use the included metal 1-inch adapter shims to mount a 1-inch tube scope. Aluminum construction, durable matte black anodized finish. This tough scope mount features a lifetime warranty.To make sure that the mount nut is fully tightened, turn the nut clockwise until resistance is encountered. After that, turn another 1/2 turn. If a torque wrench is being used, we recommend no more than 35-40 in-lbs.