Window
film is always applied to the inside of the glass. Specialist simply
using the outside of the window to cut & heat shrink the window
film for a proper fit.
Only
if you choose to install inferior films like those made in China
/ Korea. Most US quality films are guaranteed not to turn purple, fade or bubble.
Laws
pertaining to how dark you can tint your car windows are subject to
JPJ approval. (VLT for front windscreen is 70% above and VLT for rear
windscreen and 4 side windows is 50% above.)