They say:

We combined the best elements of a Tone Bender MkII fuzz with a Rat distortion to create something that sings like a fuzz but is tight like a distortion.

It loves humbuckers and single coils. It loves your cranked amp and your super-clean amp. The front half of the circuit is based on the Tone Bender MKII, widely considered the most desirable of the Tone Benders. In the original, a germanium transistor makes the signal loud. A second transistor makes it very loud. A third one makes it ridiculously loud.

The filter control works wonders, enabling shades you'd never obtain from a Tone Bender MKII.