The SME Bubble Level Anti-Cant Device boasts a streamlined eye-pleasing appearance that blends in perfectly with traditional scope rings while helping to eliminate accuracy-robbing canting errors. The easy-to-see offset level helps make immediate corrections without taking your eyes off the target. It attaches to your riflescope like a traditional scope ring; halves clamp together with two steel allen head screws. Constructed from aluminum, the ambidextrous design works for both left and right handed shooters. Note: 30mm to 1" model utilizes a spacer to be able to fit on both tube diameters.