I bought my Italian 92 Centurion in 1992. And shortly thereafter put Hogue pebble-grain panels on it.
So, hey, answering you should be easy. Just retrieved the original plastic case. And, WTF, why are the original plastic pieces not there ?
Oh, I remember. Long ago and far away I gave them to a LEO buddy who broke one of his on his service gun. Don't ask, don't tell.
OK, after getting over all the memories THAT brought back, I measured my Hogues.
One side is 1/8 " thick. Or, if you prefer, 3.175 mm. Actually, I didn't take one off to get a real accurate number. So, 3 mm or so ??
Best I can do without any work on my part. After all these years my grips may be "rubber-welded" to the gun frame.
I don't have any idea if Hogue has a current grip that is actually the same as my ancient model. Mine have served me well.
Oops, forgot to say mine are totally "flat". There is no "palm swell".