CTS 500k/250k dual concentric "stacked" audio taper potentiometer. Allows for volume and tone controls in one 3/8" mounting hole.
Top shaft (250K) is 3/16"(4.75mm) diameter and bottom shaft (500k) is 17/64"(6.75mm) diameter.
Includes nut and dress washer. Correct value for '62 stack knob Jazz Bass®.

Note : this model is suited to mounting onto a pickguard, not through a guitar body.