It's the combination of a Tone Bender MkII fuzz with a Rat distortion to create something that sings like a fuzz but is tight like a distortion, from a really beautiful singing tone, to tight, harmonically-rich crunch, all the way to fuzz mayhem. The Input knob controls the input sensitivity and adapts to all pickup types. Gain is not a conventional gain setting and controls the gain of the second gain stage by controling the amount of negative feedback in that stage, resulting in a wide ranging gain control that sounds great throughout its entire rotation. Filter allows you to dial in your final tone from smooth and creamy all the way to bright and cutting, better than the Rat's Filter control.