Ultimate Arms Gear 30 mm Aluminum Base QD Quick Detach Thumbnut Scope Ring For 30mm Tube Scope, Red Dot Sights, Optics, Flashlight One-piece, ring is precision machined to true MIL-STD Specs for a secure fit. Easily Attaches and Detaches with Thumb Operated Nuts. Will fit 30mm scope tubes. 4 steel screws secure the top ring strap to hold the optics tight under heavy recoil. Will Center of your optic at 1.5", the optimal height for co-witnessing with iron sights. A good choice for the Aimpoint Comp series and Sightmark Red Dots