The adaptor itself seems to work fine. I've used it with lenses like the Helios 44M 58mm and Helios 28mm wide-angle with much success. However after shooting with it for several days, I've noticed maybe a dozen fine metal particles covering my A7ii's sensor. I can't be certain whether the particles came from a lens or the adaptor itself, but it might be a good idea to leave one of these adaptors on each M42 lens you have, or purchase a more expensive one that won't wear.
08/05/2019
Excellent adapter, does exactly as it should. I can now use my selection of M42 lenses on the Sony A7ii the way they should be used.
16/02/2019
09/12/2018
Good machining shame wasn't the one I needed a lot of forums misleading about the adapter I needed but will use soon when have the right lenses
08/12/2018
I waned this to test my old glass on a Sony FS5 camera and it worked perfectly.
21/11/2018
Very good at this price point, just be aware that the tripod mount on this may interfere with the tripod plate of the k&f tripods and I assume other tripods, this may just be specific to the A7ii camera, I had to remove the tripod mount off the adapter which is easily done by two very small screw's, these are quite difficult to remove as require a tiny screwdriver.
15/11/2018