Just to make sure it will go the lip. 2 nuts hot glue. Can be removed when the job done.
I’m going to do the same inspection myself this afternoon, so here is the spec:
97-04 boxster-
Front: 22.6 mm minimum.
Rear: 18.6 mm minimum.
So if you are over these measurements it will tell you how much life you have left on your rotors.