Skull knob, 6mm ID for splined potentiometer.
In my experience, thermal coefficient of expansion varies between filament types. This is a tight fit that works well for silks. If you desire a looser fit, scale the model to 101%, or file/sand ID (especially the seam).
Consider posting a make, I’d love to see the colors y’all come up with.
Please see my other potentiometer knobs:
https://www.printables.com/@PanzerDesign/collections/1399185
The author marked this model as their own original creation.