I needed a knob to fit the head of a 5/16ths pan head machine screw needed for changing belts on a 2x42 Craftsman Belt Grinder. I wanted something more unique and grippy than a sphere. It can be sized up or down as needed. Stick the head into the socket in the knob, put a dab of epoxy to hold it in place and then push the sleeve over the shaft of the bolt to set it in place. The STEP file is there if someone wants to mess with it.