This is an adapter for mounting the highly-regarded UV TOPCOR lenses on EOS mount cameras. Focuses to infinity. The aperture ring moves smoothly. This is amateur-made, so there may be issues with precision and strength, but it worked without problems in the range I tested it. It worked with 28mm-100mm lenses, but I have no experience with heavier lenses of 135mm or more. The lens is a UV TOPCOR 50mm, the final model HI TOPCOR 50mm F2.0. The lens appears clear, but there may be some dust inside. The focusing helicoid is smooth. The camera in the image was used for testing and is not included in the sale.