500k Audio Taper, Solid Shaft With Nut, Lock & Dress Washer.
Dimensions - 1/4" (6.35mm) diameter solid shaft. The threaded portion on the shaft is 9.5mm long. Total length of the shaft is 18mm.
Audio Taper Pots are generally used in both Volume and Tone Positions.
Rule of thumb - 250K pots are generally used with single-coil pickups. 500k pots are generally used with humbuckers.