Most of the medium format folders with film counters, do it by counting the turns of the take up spool. If you use modern thin base film that does not work well. Foma (and the same stuff relabeled as Arista.EDU Ultra), is thick enough to work in those cameras with proper film spacing.

I have a Hapo 66e (rebranded Baldix RF), and and Iskra with film counters (Also a Kodak Monitor, but it needs a new bellows). The Hapo counts the turns and will only work with the Arista, the Iskra counts frames by picking the backing paper with a spiked wheel and will accurately count frames with everything I have tried. I like the Arista, it is cheap, and works well in all my 120 cameras. I mostly use the 100, occasionally the 400. I wish they had a 25 version as it would give me the shallow DOF in bright sun I can not get with the slower shutter top speeds on some of my cameras.