Clamp to your receiver to stop creep on hard recoiling air rifles. Black anodized, extruded aluminum construction clamps to all 3/8 and 11mm dovetail receivers and scope rails. Includes a 160 diameter hardened steel roll pin that can be tapped down into recesses in the receiver or the scope rail. Stop block can be mounted either underneath the scope or behind the rear scope ring. 3/4 square, requires a minimum of 1/2" of clearance between top of receiver or rail and bottom of scope. Requires use of High rings.