VLT stands for Visible Light Transmission — the percentage of light the film lets through. A lower number means darker glass: 5% is classic limo tint, 20% is a popular privacy shade, 35% is a clean factory look, and 50% or lighter is mostly about heat and UV rather than appearance.
In Colorado, front side windows must allow 27% or more light through, so the fronts and the rear are usually two different conversations. Most customers match a legal ceramic shade on the front doors to their factory rear glass, or go darker in the back for kids, pets and cargo.
Here's the part most people miss: with ceramic film, darkness doesn't equal heat rejection. A light 50% ceramic rejects far more infrared heat than a dark dyed film, so you don't have to go limo-dark to cool the cabin. Bring the vehicle by the shop and we'll hold real film samples against your glass in daylight — it takes five minutes and it's the only honest way to choose a shade.