The PRW2 (Perma-Ring Weaver Style) rings are based on a proven cross-slot design that provide a permanent cross-slot stability. This model has a medium ring height and a 34mm ring diameter.We've updated the proven cross-slot design of these steel rings to be stronger and to give them more contact with the base for added stability and easier installation. Features: Our cross-slot base rings are engineered specifically to match up with cross-slot bases, we recommend you mount these incredibly stable rings on firearms such as tactical shotguns with built-in mounting rails Steel rings that are based on the proven cross-slot design provide permanent cross-slot stability, uses the Leupold QRW bases or any other Picatinny-style mounting rails Bases are available for many popular rifle models