I think the higher the % the darker it is isn't it? Surely you need 30% See the attached photo of my Golf, rear is 90% front is 20% from the factoryIt said it is 65%, so probably a little dark..still not sure I like it though..maybe I'll go for a 75..a bit lighter ! and as it only costs 6 quid it's one of the cheaper spends on the pit.had a good hours fun getting it on though.
Suspect while that is important, there's an argument that it's so that the police can see the driver and their intent. Too dark and they can't.From what I understand about why front window tinting is illegal at higher levels, if you can't see the driver's eyes clearly from the outside then it's not good news. Eye to eye contact can be vital in assessing whether a driver has seen you like pulling out of a junction.