My potentiometer knobs I have 3 knobs. 15mm, 20mm, and 30mm diameters. All are 15mm’s tall. There is a ¼” round hole (6mm’s X 12mm’s) for the potentiometer shaft with a pilot hole for a set screw. I used a 6-32 drill/tap combo bit to thread the hole. There is a slot on top of each knob so you can slide in a piece of 1.75 filament as an indicator. I used white, yellow, and green for high contrast and visibility. I printed these in PETG .2 layer 20% infill

• I added a fourth knob. 30mm diameter and I hollowed it out on the under side so it uses less plastic.