VLT (visible light transmission)
The percent of visible light that passes through window film and glass.
A lower VLT means a darker window. 5 percent is very dark. 70 percent is close to clear.
The law measures VLT through the film and the glass together. Factory glass is not 100 percent clear, so the final number is lower than the film alone.
In Nevada the front side windows must have a VLT of at least 35 percent, with a 7 percent tolerance.