Here’s what Mike says…
OC81 Germanium transistor Fuzz.
Inspired by the Tone Bender MKII style circuit.
Classic sounding Fuzz pedal with the beautiful warmth and power of vintage Mullard OC81 germanium transistors.
Powered by standard 9v tip negative, sleeve positive external pedal power as well as 9v battery. An internal voltage inverter allows you to run the positive ground circuit with standard negative ground supply’