Burris XTR Signature Rings were designed for the tactical shooter. They deliver plenty of holding power, with less weight. Unique, self-centering, dual steel clamps with full cross-through connection assure proper center on any width Picatinny rail, while adding extra strength Revolutionary Pos-Align Inserts technology, in a tactical ring configuration Pos-Align Inserts guarantee perfect centering and maximum scope-to-ring contact for tremendous gripping power without damaging the scope finish Lets you virtually sight in your gun without moving the scope adjustments Corrects misalignment caused by off-center receiver holes Corrects for bases or rings being slightly off-center No need for expensive tapered bases or shimming for thousand-yard shooting Rugged, robust aluminum tactical rings save weight and mount on any Picatinny and most Weaver style rails NOTE: Each ring set includes one set of the +/- 0 MOA concentric, one set each of the +/-5 MOA and +/-10 MOA, and two sets of the +/-20 MOA. With these inserts, it is possible to make 0, 5, 10, 15, 20, 25, 30 or 40 MOA of cant in the scope mount. Pos-Align Inserts guarantee perfect centering and maximum scope-to-ring contact, so you get all the clarity, sharpness, and brightness your optic can deliver. Virtually sight in your gun without moving the scope adjustments Corrects any misalignment caused by receiver holes drilled off-center Corrects for bases or rings being slightly off center Makes expensive tapered bases or shimming for thousand-yard shooting a thing of the past