HersmayM42-EOSR M42 to EOS RF Lens Mount Adapter M42 Lens for Canon EOS R RP R5 R5C R6 R6II R7 R8 R10 R50 R100 Full Frame Mirrorless Camera

Nice no nonsense adapter for M42 screw mount lenses to Canon. Great fit, nicely built.

This adapter is awful. It doesn't fit my vintage M42 lens because it only screws on a little less than halfway. Currently my lens is using a M42 to EOS adapter that fits just fine.

This item works great. I have however with some of my extension tubes issues. I am not certain if the extension tubes have the issue or this adapter. In any case I bought lots of extension tubes 30mm, 20mm, 10mm, 15mm, 12mm, 7mm, 3mm, ... and so on that work between themselves ok, However the 20mm and 30mm do not fit on the base, luckily the 10mm did perfectly fit so I could through a combination in different order create my 50mm I needed. This allows me to put then the extension on it so I can mount my microscope lens to the RF mount via the m42 rings. So overall I am very happy. Previously I had: RF-EOS <> EOS to M42 <> then all the different rings to get the right length, so I replaced with this the EOS adapter and the EOS to m42 adapter. I will now keep this together and have now a "dedicated" solution. Originally I 3-d print the adapter from RF to RMS, but as it turned out this did not work at all as my 3-d printer did not result in a mountable adapter to RF. Instead of reprinting one to EOS, I decided to just go with this ring and the extension tubes. I am very satisfied although I gave it not 5 stars.