Spirit Bubble Level for 20mm Rifle Scope Attaches directly to dovetail to ensure bore and reticle alignment at a glance Can be place before, after, or under the scope Anit-cant - make sure your scope is absolutely level Can be used on real fire caliber as well as air rifles Shock resistant Compatible for 20mm lead rail Specifications Dimensions: 2" x .25" Weight: 0.5 oz Material: Aluminum Alloy Finish: Black Matte Items Included One Bubble level One Allen key