I think Numrichs doesn't measure their grip caps, they just take it off a Savage 99 and throw it in a bin that says "99 grip caps" on it.

You probably got one off a 99R which were larger.

I think if you sent it back and gave them the measurements of the one you need they could hook you up with a correct one.

I've got plenty of R's here and an EG but I don't have an F to give you a correct size.