Small fidgetring witch I originally made for my wife.
Inner diameter is 18mm
I will adapt it to your size!
My Printsettings:
Layerheight: 0.16mm (i think 0.2 should work, too)
Wall count: 4
Top/Bottom surface pattern: Concentric
You can try to print with concentric infill but in my case there are some “dots” with “internal solid infill”. The cleanest print in my case was with the settings mentioned above.