Wow, I'm surprised at the responses actually. I thought most people would say to use the relays. I read some info. that scared me a bit. As the ballasts age, they tend to draw more amps on initial start up. As this happens, the stock wires can fail or blow fuses. The relays eliminate this possible problem by using an inline fuse and the relay (of course). So, in theory, the inline fuse will blow before anything happens to the stock wiring. I bought a complete plug N play harness on ebay for about $30 bucks. Pretty cheap insurance if you ask me.