Leupold Mark 4 rings are machined from solid steel they offer superior integrity and tighter tolerances that are based on the proven cross-slot design. Use Leupold PRW bases or any other Picatinny-style mount rails. Use as a high-quality alternative to ingmounts sold by firearms manufacturers and as a no-tap mounting method for most .22 rimfire rifles with a 11mm 13mm or 3/8" dovetail rail. Because these rings are machined from solid steel they offer superior integrity and tighter tolerances.