M39 to EOS Adapter with 50mm Extension

This adapter is designed to mount a 50mm enlarger lens with an M39 thread onto a Canon full-frame DSLR for 1:1 35mm film scanning.
The M39 mount uses a screw thread, so you can fine-tune focus by rotating the lens.

Although Cura may show it as “not watertight,” it prints just fine for me.