Burris Signature Zee 1" or 30mm Rings fit any Standard, Dovetail, Double-Dovetail and Weaver Style bases and use swiveling inserts for perfect scope alignment. The basic 1" rings come with neutral swiveling inserts that self align with your scope for stress free, perfect alignment of the scope and rings. The 30mm rings come with "Zero" inserts and +/- .010" inserts for both front and rear rings. The optional 1" Posi-Align Offset Inserts allow you to use the rings to sight-in for the sweet spot of your scope. Scope Sweet Spot - The best possible optics and optical correctness is achieved when you can view through the center of all of the lenses in your scope. This occurs when your windage and elevation adjustments are set to the absolute center or middle setting. The more you have to adjust windage and elevation to sight-in your scope, the further you get from the sweet spot. Posi-Align Offset Inserts - These are inserts that have off-set centers. The set includes one each for 5, 10, or 20 units of offset. This amount of offset along with the ability to swivel the offset, will get your scope within 3" of zero without adjusting windage and elevation. Then, just use your windage and elevation adjustments to fine tune your zero for differences in ammo and conditions.