This fisheye is a lens element on the lansbaby system. It’s an “effect lens” system that’s a bit hard to explain here in few words, but imagine to have different mounts, fixed, focusing, tilting etc, then you have different lenses to fit, you change aperture swipping a disc within the mount and the lens. The images on top show the lens on the simplest mount called “Scout” and on the older version of “Composer pro” tilting mount