This is a powerful little bullet-type power source. It is special in that it can give power through a cable to an accessory, or be a bipolar power all by itself in your hand for a truly unique massage. It's approximately 4 in x 2 in and uses a round 3 V battery (included). It uses 2.5 mm plug lead wires available in Pins or Snaps with 2 or 4 leads. Each kit will come with 1 set of Lead wires and 1 sheet of corresponding pads.