500K Audio Taper, Split Shaft With Nut, Lock & Dress Washer. Vintage Style 'Dish' Back with US thread and 24 spline.
Dimensions - 6mm diameter split shaft. The threaded portion on the shaft is 9.5mm long. Total length of the shaft to the top of the spline is 16mm.
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.