Tuned & Hardened For Lasting Performance Machined with exacting tolerances hook is .005" closer to rim to give a positive, non-slip grip on the case head. The very precise hook point is hardened to Rc 58-60, will not lose its edge, even after years of use. SPECS: A-2 tool steel, in-the-white. Fits Ruger MKII, MKIII, MKIV and 22/45 pistols 10/22 and 10/22 magnum.