4-screw Medium Profile "Tiger" Ring * Precision Machined from Aircraft-grade Aluminum Alloy with Anodized Black Matte Finish * User Friendly Quick Detach Lever Lock with Full Adjustability to Fit on any 9-11mm Rail * Innovative Robust Recoil-proof Spring Tensioned Stop-pin for Rails with or without Recess Holes * Spring Tension Controlled Locking Plate with Steel Insert Guarantees Most Secure Installation