Proco Fat Rat Distortion Pedal With Vintage And Mosfet Clipping CircuitsClipping Section: Switchable between stock silicon clipping, as in the classic Rat, and a mosfet germanium clipping section, which is entirely new to the Rat line. The mosfet clipping section gives you subtle scoop and smoothing in the upper mids throughout the entire gain range of the pedal, and makes the pedal sound more amp like and natural. Thick Switch: Provides a significant bass boost and simultaneous hi cut this makes the pedal more suitable