the darkest ive seen is 2.5 %, but 0% would be like way to dangerous for night driving, but i have 5 % on the side and my rear window is 15% and front windsheild is 35% with 5% strip across, i tinted the front because i live in florida and so much sun and heat comes right on your lap through that windsheild and even with the air on, your still gettin fried, boy did that help alot, it gets freezing cold in my car. plus i like the security and privacy.