This one is a nice antireflection-coated assembly with an integrated gear for focus automation. It sports a 20 mm focal length and 10.7 mm clear aperture. The mounting consists of a threaded brass collar fitted into a plastic housing. The lens assembly is threaded and can be rotated for focusing by means of a 37 mm diameter, 70 tooth gear. The gear face is 1.6 mm thick. The usable travel of the focusing mechanism is approximately 6 mm. Unused. We only have a few, so act fast!