I already ran wires to a trailer I was doing but wasn't happy with the wires I used so I tore them out and used these CZC trailer lights. The only thing I used of my own was water-resistant connectors I have since it did not have enough on its own but either was not a big deal to have to go buy a couple of connectors if it's how you want to do it. Great quality and very impressed

Some newish vehicles (last 10 years) have an option in main ECU to specify if regular or LED bulbs are fitted ? Only ever seen it on one car, but cannot remember for sure. I think it was my dad's Ford Focus ?