28/04/2019
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.
03/05/2018
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.
11/02/2018