The Fuzzy Wooly Bear is available as a PNP Silicon overdrive unit or PNP Germanium overdrive unit. The Silicon version of this unit has two knobs on top, one gain and one volume. All silicon FWBs sound mostly identical. These pedals have a beautifully textured gain structure that allows wonderful light grit to raging distortion. The Germanium version of this unit features two knobs on top also, one for bias and the other for volume. The bias knob does just that, adjusts the bias voltage of the germanium transistor. This allows the user to get a range of sounds and is most noticable on the decay of the note. If the bias is set too low or too high the decay will sound drastically different, from a ratty, ragged decay with sharp cutoff to that of a beautiful standard note decay this pedal can do it (if set to full max or to zero, no note will be produced, as the transistor will not be able to operate). The volume knob, as usual controls pedal output. The Silicon version is more aggressive in comparison with the Germanium with the Germanium having a slightly fatter sound than that of the Silicon.