I was going to say .146 on the rear which is what my m-17's have , but I went to the safe and measured my 617-6 4" and the rear looks about .126 and the front is the hi viz replacement made for the 617 and that is .165 . Does your front sight measure similarly ? You could go taller in front . I found Midway USA had a pretty fair selection of replacement rear sight blades,screws and nuts last time looked .