just got mine tinted (crew cab) and the back was 19% on my meter, so I went with 20% and it matched really good. the front windows do meter at 70% with no tint though because of the factory glass.

 

see i figure why even bother with 20 you get an extra 5% going with 15% tint & the law gives you +/- 3% difference (varies with state law) in FL the legal limit is 18% & at our shop we recommend 15% rear 30% front