Simple overdrive pedal with 2 settings and 1 switch for a vintage or more modern drive sound. Caroline says it 85% drive, 15% fuzz. Output (left): output volume. Grit (right): amount of drive. Style (switch): vintage or modern. Crystal Lettuce (internal): sets the voltage of the BC108 transistor to fine tune the minimum gain and maximum range of the device, set to 7 Volts by default.