This is a Chinese-made M42 to F-mount adapter with infinity focus correction. It's a typical, inexpensive product. As reviews from others suggest, this product has quirks and can be finicky depending on the lens. With my Takumar f1.8/55mm, infinity focus was slightly off. Also, close-up shots were soft focus unless I stopped down the aperture significantly (when mounted on a D610). Apparently, some other M42 lenses work fine with this adapter, but I only own the Takumar, so I don't know the details. Please refer to product information on Amazon or similar sites to make your own judgment. Thank you for looking.