Ressurecting this old thread because I'm finally getting around to this project. Brownells has me confused. They have S&W W/O rear blades listed in .126 and .146 height. I also see a black rear sight listed for compatible with the 617 in .136 height. I have a 617 no dash with 4" tube (thanks Gary). I need to order a W/O rear sight tonight. Do I go shorter .126 or taller .146? Also, is this measurement for the overall height of the blade, or just the notch cut in the blade? I do not have any sort of measuring device I would be confident using to judge a .02 difference in height to measure what is now on the gun. To add to the mess, I'm changing out the front sight to a Hi Viz F/O at the same time, but it appears to be a match for the same height as the current sight.