12v 500mA wall transformer. Can be used to power the MegaSquirt Stimulator. Recommended when using the Stimulator with MS II, as a 9v battery only lasts a few minutes.The power plug fits the jack on the v2.1 Stimulator. To use this with earlier versions of the Stimulator, the power plug must be cut off and the wires inserted into the terminal block.120v AC input for US and Canada only.UL/cUL Listed.