Want to turn 9v into 18v? This is how! I bought the last one of these a few weeks ago and decided that I no longer need it. It is basically a special battery clip that has some kind of resistor to double the voltage of a 9v, but drains the 9v quicker. I will post pics later. It is brand new, and comes with detailed instructions on how to install with or without a battery box. Asking 55.00 shipped to 48 states.