Cat. No. Used-Retro-TD-2023
The retro or reversing adapter maintains all electronic functions of the lens while allowing it to mechanically mount to the camera in reverse. The purpose is to get higher than 1::1 magnification and by reversing the lens you can do this. The 80/2.8 and 120/4 lenses are excellent options but the 60mm also works well.
There are several advantages to using the reversing adapter over a long extension tube: You don't lose as much light, images don't suffer from diffraction effects from extension and the lens + camera system is shorter.
I have also built myself a number of interesting devices for tilt and shift using the retro ring to pass the electrical signals to lenses mounted off the camera.
So there are a number of uses for a retro adapter... if you do product or macro work you should have one.
