My new (to me) S&W 25-5 is a 4" gun and it has a plain black rear sight blade. With my 1/2 blind eyes, I need a white outline rear and Smith&Wesson offers them with 3 different heights-.126, .146, and .160. As near as I can tell, you really need to break the screw and remove the adjusting screw and remove the rear sight blade to measure it. I would like to have the new one in hand when I do this. Does anyone know what height a 4" 25-5 should have? Thanks