Gone are the days of touching the bushing inappropriately to guess the diameter (or sort them if you're WEIRD!!!!!!) These are the FUTURE!!!! I DUMP them on my table, LOOK at the number, PUT the size I want on my gear, PUT another one of the same size, REMOVE it because I need to use the .2 instead of two .1s, and THERE you go, super easy awesome shimming !! ! ! ! Note: I've seen that after a bit of shots through my gun the number starts to fade, so be careful