Phone plug with positive tip 9V DC 100 mA. This molded power supply works with these pedals: Nano Small Stone Nano Clone Nano Dr. Q Nano Bassballs LPB-1 Pocket Metal Muff Muff Overdrive Little Big Muff Micro Metal Muff Micro Q-Tron Stereo Pulsar Clone Theory Metal Muff Soul Preacher Holy Grail + XO Octave Multiplexer #1 Echo Stereo Memory Man with Hazarai Micro POG Knockout Stereo Electric Mistress Germanium OD Holy Stain