Knob for d-shape shaft. It has an internal taper so the edge of the outside reached almost flush with the surface the rotary encoder or potentiometer. It is symetrical so has no indication of direction.

It fit on fine first time for me.

The shaft is about 6mm/ made to fit 6mm shaft.

Check out the remixes if you want a round shaft (without d) or versions with a mark to indicate direction.

Print with the rounded /flat end on platform.