Encoder Knob - 6mm flatted shaft

There are others out here in Thingiverse but all were too loose on the shaft of the encoders that I had. Mine have a 6mm shaft with a 1.5mm set back flat.

My settings (in Makerware):
10% fill
2 shells

I had to take an exacto knife to clear out the shaft opening but in the end I had a good snug fit and it works great.