Electro-Harmonix Pocket Metal Muff Distortion Pedal Volume knobDistortion level knobMid frequency selection switch The Electro-Harmonix Nano Pocket Metal Muff Distortion Pedal takes the most powerful features from the popular Metal Muff and artfully squeezes them into a slick, die cast aluminum housing Switch-selectable mid frequencies offer powerful scoops With separate knobs for volume and distortion level, and a red LED indicating whether effect is on or off Works with a 9V battery or optional AC adaptor