Set of two generic black preset roller knobs. Center hole is bored for import 6mm* solid shaft Alpha style pots. Hole for the pot shaft in this knob measures exactly 6mm. 1.5mm Allen head set screw for fixing this knob to the solid pot shaft. I measured 24.93mm diameter, 5.70mm thickness. *I measured 5.95mm on the shaft of the Alpha pots in our stock. Sale is for knobs only, pots are shown as illustration of how the knobs are used. These knobs are metal.