Got the M&P rear sight today, old one came off with the delrin punch and the M&P sight went on the same way. I used my sight pusher to slightly adjust it and check with my laser bore sighter only. It didn't have the set screw, but I have a ton of those sitting around and had the perfect size that sits flush with the top when tightened. The set screw can be had at any hardware store in size 5/40 3/16"L or from S&W direct.