2pcs Outdoor tactical equipment 25.4mm high profile sight installation ring 11mm optical sight base 1.Design in hollowed-out configuration between the ring and the bottom of the base, to release heavy duty when clamping your scope. 2.Built-in tape inside per rings to prevent from marring the scope, also prevent sliding and holding postion accurately. The ring is for most scopes which are in 1''/ 25.4mm scope tube. High profile, 0.98'' gap from base of mount to bottom of rings. ( Item height: 2.1''). 3.With only 1 rail clamp screw and 1 scope clamp screw per side, just twist off the nut and mount the base on the 20mm rail easily.