Reversible locking plate to fit full range of airgun .22 rails. 1" diameter. 21mm width. 4 Hex screws on top to tightly secure the scope. Precision machined from aircraft-grade aluminum alloy with anodized black matte finish. Complete with Stop-Pin for rock solid application. Ring base designed with locking Hex screws to tightly fit on mounts with airgun .22 dove-tail dimensions.