This is a Anti-Stress Ring or fidget toy I made.
For the smoothest rotations you should print this in ABS or any other smooth material.
It also prints well in PLA and PETG but the friction will be higher.
It has an inner diameter of 17mm.
If it doesnt rotate after you print it, check your printer settings for any problems.
This is a print in place ring so it does not require any assembly!