Since only a step file was supplied, I used an online converter to convert to stl. I normally don't use rafts, but the first one jumped the bed. Added raft and worked great with linear supports. Using the Flashforge slicer. (edited)

Worked great. My printer/slicer starts each layer at the same spot, so there was a bump I had to trim on the inside of the round part. I initially tried screwing the lenses on which was ok, but difficult to get straight and more difficult to remove. I ended up just printing 4 of them (one for each lens in the diopter kit) and pushing the lenses into the print which worked very nice but good luck getting them out. lol. Fits nicely on the camera too, though part of me wants to put a little tether so they don't fall if it gets bumped off. Either way, 5 stars.