MXR M66S Classic Overdrive Guitar Effects Pedal Output and gain controls for ultimate control at any volume Simple footswitch toggles effect on or bypass It can be powered by one 9-volt battery (sold separately) or Dunlop ECB003 AC adapter (sold separately) MXR's GCM66 Classic Overdrive makes sound simple, adding sustain and gain without coloring your guitar or amp's tone and is housed in an indestructible die-cast housing It can be powered by one 9-volt battery (sold separately) or Dunlop ECB003 AC adapter (sold separately)