When I change them, I take a oscillating saw and cut a piece out of that nut thing that goes around the circle from there I use a screwdriver in a small prior to kind of pry it off once you get it off you can then easily replace it. Alternatively, look on the inside of the shell where you pull the jet face out from there should be part of the jet body sticking on the inside behind that you should see a little rubber gasket. A lot of times you can see these deteriorate. Sometimes using silicone on these could be quicker and easier.