It would be helpful if you could post a photo.
The info I have for the originals (1966 production) are two sizes of 'tumbler', 15cl and 25cl (also a punch cup 10cl),[from Oiva Toikka, Glass, 1988].
There quite a number of different glass sizes introduced during the 70s. Be aware that the Arabia thing was just marketing - the glass was still made at the Nuutajärvi factory as before, just different boxes and labels.
Are yours clear or coloured? That can be another clue.