I built this for a school project faire. It has slots for different size coils so I am not limited to one barrel. It has a custom built control box with: Power, HV in, 2 switches to control which capacitor bank to charge, and a firing switch... As you can see I also made the power supply too. I bought the metal case at fry's electronics down in burbank, CA. It has a power indicator and charge indicator LED to tell when the capacitors have reached maximum charge. It takes about 30seconds for one bank to charge. Each capacitor bank consists of 6 330VDC 120uF flash capacitors.