Window film technology
Window Film Mil
A mil is one-thousandth of an inch (0.001″ ≈ 25.4 microns); window film thickness is commonly quoted in mils, with solar film at 1.5–2 mil and security film at 4–14 mil.
Mil thickness sets the film's mechanical robustness. A 2-mil solar film is fine for heat control but offers minimal glass-retention benefit. A 4-mil security film starts to provide real fracture resistance. Multi-layer security films at 8–14 mil are used for blast mitigation.
For automotive solar applications, 1.5–2 mil is the standard. Thicker isn't always better — thicker film is harder to install around tight curves like the rear windscreen of a coupe.
For residential and commercial security film, mil thickness is a critical spec — see our architectural film guide.