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.