VLT (Visible Light Transmission): This refers to the percentage of visible light that can pass through the window of your car. North Carolina State law requires a VLT of at least 35% on all vehicle front windows and car/sedan rear windows. SUVs, Vans, and Trucks, can all have any VLT on their rear windows.
AS-1 Windshield Tinting:
The AS-1 line is located on the top edge of your windshield. This line represents the lowest you are legally allowed to tint your windshield with non-transparent window film. Above this line you are free to use any darkness of tint.
In North Carolina, it is not legal to tint your vehicle with the colors Red, Amber, or Yellow. These colors are restricted on all windows.