In the words of Fish Circuits:

The Fish Circuits MODEL ONE is a classic natural overdrive with spicy tweaks. Incredibly versatile and more than usable on just about any settings. At lower gain settings, the MODEL ONE will give you dynamic amp-like breakup tones, that react to the subtleties of your playing. When cranked, you will find yourself in a saturated fuzzstortion territory, with loads of sustain and depth, reminiscent of citrus-colored amps.