The Primary Arms Deluxe AR-15 Scope Mount is ideal for M4, AR-15, and similar "flat-top" 1913 Picatinny mounting platforms. Aluminum construction, durable matte black anodized finish. 2.52 inches of clearance between the rings. Places the center of your 30mm tube scope 1.5 inches above the rail. Fits scopes with 30mm tubes. This tough 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.