As far as I know there are two sizes that should be the same across brands 31/32 and 7/8. They are poured into molds if I'm not mistaken.
Sometimes one hole gets sanded more than the other so the insert goes in without resistance or "pinching". Just remove the insert and sand the hole slightly then put back in. Remember that we're also drilling into various densities, and the bit can have variations if the driller tries to hurry, or bits get dull.