Actually, it's the lighter, higher performing films that provide the most protection and look the best on a car. The lower the percentage, the darker the film and the more privacy it offers. Most states permit some tinting on the front side windows, usually from 35 percent to 50 percent light transmission. Back side and rear windows are generally allowed darker tinting, provided the vehicle has left and right side view mirrors for visibility. Anyone planning to tint a vehicle should consult with state police or the film manufacturer to determine the exact level of light transmission permitted.
Window films are also available with different performance features.
Economy window films are constructed of dyed or coated polyester and offer good UV and glare protection, but little heat rejection or durability. The next level of performance is scratch-resistance. These films offer the same benefits as economy films, but add an anti-scratch coating that keeps the film looking good longer. The best heat rejection available comes from metallized films. Metallizing a film does not make it dark and shiny, but increases the active heat and rejection.