What Line 6 has to say:
Tough enough for arena stages yet small enough to fit in your backpack, FBV Express™ MkII delivers a crucial collection of hands-free functionality that will keep you at the foot of the stage instead of tied to the front of your Line 6 amp or POD®. FBV Express MkII delivers out-of-the box, plug-n-play connectivity. Stomp the four steel footswitches to quickly store and select channel presets, synchronize your time-based effects with Tap Tempo, activate the chromatic tuner, and more. When paired with most Line 6 guitar amplifiers, the footswitches also give you total control of Quick Loop, the amps' built-in 14-second sound-on-sound looper. The burly, full-sized volume/wah pedal feels solid under your foot and features plenty of grip. Clicking the toe-switch toggles between volume and wah control (with an illuminated LED to match). The bright and easy-to-read LCD shows tap tempo, active channel and the chromatic tuner (when activated).