Ortofon mono cartridges

There are two different versions of the venerable Ortofon SPU "G" mono cartridge: SPU mono GM/25 and SPU mono GM/65. The 25 and 65 refer to stylus diameter. Can someone help explain the different applications to me? I believe the type 65 is for vintage records, while the 25 is intended for more contemporary mono records. Am I correct?
Stylus diameter for 78 rpm was larger. I think that all 33 rpm, mono and stereo, call for the smaller diameter.
I was afraid of that. I just obtained an SPU GM/65, believing it was a 25um version when ordering. So, basically, the 65 is the wrong tool for the job.... Thanks for your input, Eldatford.

bty, will using the 65um stylus damage my 33rpm LPs?
It certainly won't track properly, and I would expect damage.
ok, thank you. will return to Germany, to exchange for a GM25.