Different grades of window security laminate and window film are often categorized by their thickness which is measured in an Imperial unit of measure called mils. One mil is one-one-thousandth (1/1,000) of an inch. Note: a mil (which is an Imperial unity of measure) is not the same as a millimetre (which is a metric unit). Practically speaking, a 14 mil film will be about half the thickness of a credit card.
Manufacturers and suppliers often refer to the grade of a window film by its thickness. The implied assumption is that thicker is better AND that all films and laminates of the same thickness work the same and are just as good as the next.
This is not necessarily the case.
Why? There are several factors that contribute to performance and strength once a film is applied to a window.
Factor #1: The quality of the adhesives used. Good quality adhesives will stick better and hold the window together longer when under attack. The best quality adhesives such as pressure sensitive adhesives bond best to the glass and actually absorb and distribute kinetic energy.
Factor #2: The quality of the polyester (PET) used in the film. Simply put, the best quality PET will combine all of the best aspects of clarity, flexibility and strength. Often, there is a trade-off between flexibility and strength. The trick is to find the best balance of these two performance factors.
Factor #3: The laminate is designed to absorb and disperse energy. A true window security laminate will be comprised of multiple plies of PET. Each of these plies will be aligned in a manner that best optimizes the absorption and disbursement of kinetic energy. While unseen to the naked eye, this alignment is a critical performance factor.
All of these factors work together to optimize performance. Just because a window film is thick does not mean it is architected and assembled with these other design considerations.