25% is Texas law FWIW

Texas Window Tint Law - TintCenter.com

I have 30% on mine and it looks much darker than most cars with 30%. Mainly due to the small windows on the z and the dark interior.

I have 25% and love it but I also went with ceramic tint. It makes a huge difference between the wifes car and mind. She has normal tint and you can feel the difference in heat when you get into the car.

i got 40% on the doors and 20% on the rears on a mag black, i love it

I just got back!! install went great. I payed 180 cash for the job 15% all around. Not to dark and I can still see perfect. He offered to tint my entire windshield for a extra 80, but I turned it down.... for now (;

My friend has 5% all around on his firebird, I drove it once at night, super hard for me to see out of, and I felt very unsafe.

I'd never do that on my side windows, but it should be fine for the rear, I use side mirrors 90% of time for normal driving and about to have a back up camera anyways. :tup: