Fender TBX Treble Bass Expander Tone Control Potentiometer Kit The Treble Bass Expander (TBX) is a detented, stacked 250K / 1Meg control that enhances your tonal palette It functions as a standard tone control from 1 to 5; after 5 it decreases resistance, letting more bass, treble, presence and output flow to your amp No battery necessary Each TBX Tone Control comes with a .022mf capacitor, 1/4 watt resistor, white tone knob, mounting hardware and installation instructions