This official Fender TBX Treble Bass Expander Tone Control Potentiometer Kit is a stacked 250K/1Meg CTS pot. It functions as a standard tone control from 1 to 5 (rolling off high frequencies as you turn it down), after which it adds bass and treble, increasing brightness and presence as you turn it up. This is the same control that is used in the first (upper) tone knob of the Eric Clapton signature Strat. It has a centre detent in the rotation so you can quickly find the start of the TBX function and is a passive control, no battery necessary. The kit includes a white Stratocaster tone knob, 0.022 uf capacitor, 82 kΩ resistor, all mounting hardware and a wiring diagram.