This is just a shim that was needed in my case for the iris to work properly.
There are no special print settings, I used 0.3 mm layer height.
The material doesn't matter.
After printing check for any bumps or defects and sand them. You want the smoother side of the print touching the leafs.
It has to be glued inside the outer ring that has the tracks. Everything must be aligned: the iris “eye” and the tracks.
The author remixed this model.