Review on Fotodiox Lens Mount Adapter, M39 (39mm x1 Thread, Leica Screw Mount) Lens to Leica M 📸 Adapter with 28mm/90mm Frame Line, Compatible with Leica M-Monochrome, M8.2, M9, M9-P, M10 and Ricoh GXR Mount A12 by Guled Hamilton

When I got mine in the mail the clip on my M6 that holds the lens/adapter couldn't fit. Upon careful examination, it was found that the groove intended to engage the clamp was 1-1/2 millimeters longer. Aggravating. Luckily I have a Dremel so I sanded the groove a bit and now it snaps into place. So overall for the price it works. Just annoying that I had to process it further - something that should have been tested and fixed beforehand. I also got an M39 adapter for Leica M with 50-75 frames. It worked great. The difference in frame line choice, however, lies in the flange that sits over the notch. However, the 28-90 flange closes the groove and is more difficult to machine.