Works great with my Canon FL 58mm f1,2
Just had to leave a review to correct a previous reviewer, this does work with FL mount cameras too. There is indeed an obstruction from the aperture pin in the Urth mount with a couple FL lens that have a slight different shape in the mount by the rear element, but that pin is used for quick focus checking (originally with old automatic cameras).
The pin can be unscrewed with a small screwdriver like you would use for electronics (CRV+2.5), and will no longer interfere with the lens.
To use the aperture you use the two rings at the end of the lens (one has the aperture number and a dot, the other is unmarked except for a dot). Rotate the aperture ring to what you want and then rotate the unmarked ring to align the dot, and the unmarked ring will actuate the aperture with a slight twist from there.
Great build quality and price on the mount itself and happy with it, other than future designs could probably try to reduce the need to remove the pin.