This is a knob for a slide potentiometer. If you've ever had to locate a source for these kinds of knobs, you know that your options are limited at best, ridiculously expensive at medium, and totally absent at worst.
Well, with a 3d printer (and optionally, the awesome Jetty firmware,) you can save $1-4 for each knob you print yourself.
The wiper on my faders measure 4mm by 1.2mm. My project uses kind of a lot of these crammed together, so almost all of the standardly available options I was able to find just don't work. Too big, too wide, too ugly, wrong style... So here's my fader knobs. As needed, I will update this thing with different styles and sizes.
Jetty's firmware allows you to print from the SD card, which I would recommend you do. Print raftless if you can. If you do that, you can print the first three layers in one color (pause at Z axis 1.2mm), switch to a contrasting color, then print a couple of layers (pause at 1.8mm) and go back to your original color. If you want. :)
as far as print settings go, I printed mine at 1 shell, 100% infill, at 60mm/s, and you can see how nicely they printed. I tried to reduce the infill, but ReplicatorG was failing out for some reason. So I just set it to 100% infill.