"Burris Optics 626024 1"" Signature Pos-Align Offset Insert Kit includes 10 each of +/- .005, +/- .010 and +/- .020 Eccentric Offset Inserts. Burris Optics Signature Riflescope Rings also accept Burris Optics Signature Pos-Align Offset Inserts so you can virtually sight-in your gun without moving the riflescope adjustments. Lens systems perform at their optimum when all lenses are optically centered. By keeping the internal optics centered, you'll see through the riflescope all of the clarity, sharpness and brightness that the optics designers intended for you to see. This Burris Optics Pos-Align Offset Signature Insert also correct for any misalignment caused by receiver holes drilled off center, or the bases or rings being slightly off perfect center."