I'm looking to purchase a DIY ceramic coating for my M3, and I'm leaning towards Gyeon. There seem to be quite a few ceramic coating products from Gyeon, so I was looking for some input on which to choose. I've been detailing my own cars for years, but I've never done any coatings before. Also, how much product is necessary for the M3? Given the glass roof, and I don't plan on using the coating for the roof, I assume the smaller 30ml bottle would be plenty.