If you upgrade to the micro Swiss direct drive kit for the Ender 3, this is a extruder knob that re-purposes the original brass extruder gear for the knob. I was tired of most extruder knobs that only have plastic as the contact point and therefore can be rounded easily.

As I wanted it to be really strong, the brass fitting needs to be heated before it can be pressed in to the knob. Heat with a torch with a couple minutes and press in. After it cools, simply attach using grub screws.