A volume/tone knob for guitar... endlessly customizable because you add the last component - your favorite bottlecap. The knob is shaped so that caps can be pressed on and fit snugly. This model is for 6MM potentiometer shafts and has 6 ridges in the shaft opening to fit snugly on coarse-splined, fine-splined or smooth shafts. In case there's any looseness on a smooth shafted pot or after placing/removing it a few times, I added a side shaft sized to fit 6-32 x 1/4 set screws. These have been used on Gibson, Epiphone and Squier guitars so far with no problems, but please double-check your potentiometer shaft size before ordering. If there's a demand for 1/4" shafts I'll post an alternative version of this knob.
Additional detail at: http://www.twoshay.net