Confirmation of the autofocus works perfectly, I had to grind a little outside diameter because my goal (Mamiya Sekor) has a housing side with coupling ring finger, I did not want to remove the finger on the lens, so I filed down to fit the ring. Operation is no problem, the focus with 5DII is easy even with the diaphragm closed to f5.6 (if one does not want to handle the constantly), the rendering of images is superb despite the age of the goal! (1976). If you have good goals M42 I advise you that ring.