I have the medium wheel, the fine and the extrafine.
I have a problem with it leaving tracks on the ring.
The medium does a very good Job for lapping
I do have some issues with the blue(fine) and the pink(XFine)
To be clear It seems to work well on gold, but on silver I just can win.
I would be delighted to hear about your experiences with these wheels and/or the Felt Lap wheels.
P.S I am an Apprentice, and I do Pave and CAD work