Electro-Harmonix Nano Double Muff Fuzz/Overdrive Pedal Two Muffs in a Nano-sized pedalOperates in Single or Double Muff modesSimple control setone knob for controlling the level of each MuffTrue bypass Electro-Harmonix paired two of these together in one box to create the Nano Double Muff Use just one Muff for a hint of milky distortion, or cascade the second Muff for over-the-top overdrive that turns the milk into cream In single mode, the amount of overdrive will lessen as you decrease the volume on your guitar You can compensate for this by increasing the volume of the single Muff