Made of steel, it allows focusing to infinity.
This adapter is for use with some M42 mount lenses with an outer diameter of about 51.00mm screw mount and a depth of 8.20mm or more on Arri PL mount cameras.
This way you can mount any lens that is reasonably narrow at the rear - less than 51.00mm in diameter.
All 4 bayonet tips have cutouts for 4 mounting positions (for example, you can position the lens index mark on the other side for the assistant to work).
Weight - 60 g.