Just as an FYI, some people may experience problems when using their factory wiring to charge the ballasts. You may find after using them a half-dozen times or so that only 1 headlight turns on, and you may be tempted to think you have a bad ballast. What you may need is this:
It's a harness that allows the ballasts to get thier juice straight from the battery, and not through the inadequate factory wires. For $30, I'd highly recommend it.