Over the years I have bought and sold at least three Colt Ace pistols, Peters Stahl, Kart, and Kimber conversion units and have always been disappointed in the function and/or accuracy. I have finally found a 1911 .22 conversion that has it all. Bob Marvel has a unit that is reliable and accurate and pure fun to shoot. It functions with standard and high velocity ammunition. Check it out at http://www.marvelprod.com. I bought the iron sight and scope mount ribs and use an Omni 4 Dot sight. I also bought the compensator to duplicate my Open gun for practice and Bob made a fiber optic front sight for the iron sight rib. Bob even makes basepads for the converted Ace magazines, as well as a magazine loader. The conversion works with any 1911 frame. If you have ever wanted a reliable and accurate .22 1911, but were disappointed with available units, buy and enjoy one of Bob's units...you will not be disappointed.