I have 15% all the way around. I love it, cops hate it. Whenever I see a cop I roll them down. Pain in the ass, but it's worth it. I have had the tint for 2 years, in the time I have had around 5 tickets or so for it. All of which I have successfuly beat in court except one (only because they didn't send me a notice to appear and just found me "guilty".) I have a prescription but IL is changing the law so that isn't going to work anymore after 2008. I think they need to change it so we can have 35% all the way around, that would be harder to enforce though. I also think it should be a federal standard and the same in every state.
