none. but usually if stay at 35% or higher they won't bother you. i used to have real dark on my mustang 5% back 3 windows and strip across front, 15% on doors, and 35% on top of 50% down the windshield, very dark, it was fine for me, but you could not see inside the car from any window when it was dusk out, looks awesome inside and out though. needless to say i got pulled over a few times in that car. then on my M3 i got 35% black onyx all around and 50% down the windshield, has a very clean look to it and you can see right through it, yet it looks tinted, looks awesome i will post pics soon. and i have never gotten pulled over in my M3. so i would say go for it. 35% on every window including windshield would be bad ass.