Didn't think of filing this because the 4 pieces were already very thin!
WCCC Response:
This is an exact fit for ALL used mirror nuts (bezels) and the 1970 - 1973 reproduction mirror nuts (bezels). However, you will find it does not fit our 67-68 repro mirror nuts (bezels) and will need some filing to be able to work on these mirror nuts (bezels). We, and countless customers, have been able to successfully file this down enough to make it work with the 67-68 reproduction mirror nuts (bezels).