-PERMANENT SOLUTION: One-time fix remains in pistol to prevent future reassembly difficulties. -INSTALLATION: Quick and simple: requires no special tools or experience. -COMPATIBILITY: Ruger MK series and AMT pistols. Ensures proper fit and function. -FUNCTIONALITY: Prevents hammer strut lodging under cross-pin in handle during reassembly. -VERSATILITY: Works seamlessly with all aftermarket MK modifications. -NOT COMPATIBLE WITH ANY 22/45 MODELS. FITTING MAY BE REQUIRED FOR 1965-1968 MK I models, sn 334991 and above. FOR COMPATIBILITY with MK I models from 1970-1976 (sn 10-62885 through 13-49225), CONTACT MANUFACTURER. -Made in USA. Veteran owned and operated.