For those that don't understand the industry coding numbers.

The visible light transmission is a film specification that denotes the amount of light that we see that passes through a given film.
If you have a 20% film, it actually means you are losing 80% of the normal light that should be passing through clear automotive glass.....effectively the same as wearing sunglasses at night whilst driving.

Should another motorist pull up beside you and is intent on looking through your car's windows, then his vision is not only compromised by a 20% or less light transmission film, but then take away 80% of what's left as he is looking through a double layer and the rest is self explanatory as to why it's illegal for all and sundry.

University tests do in fact confirm that these films are deemed dangerous and irresponsible for automotive applications and why I don't nor ever had installed these types of films.