Law in Cali allows whatever % tint you want on the rear windows. No tint on Windhsield, or front doors. Of course you can find places to tint them for you.
True mirror tint is not allowed either but I think people are referring to the titanium look tint. Chekc out a Lexus RX300, they have a titanium look to there rears. Definitley more metallic looking.
On Thursday you can see mine. Running 18% on the rears and 35% on the fronts. Llumar black.
