2-Ply window film is a window film that has two sheets of polyester, and so in it's simplest form will be a scratch resistant coating, two sheets of polyester, an adhesive and then a backing liner. This will only produce a clear film and so very often a dye or metallized layer will be sandwiched between the two sheets of polyester to provide a colour, tint and/or solar control properties. Having a 2 ply window film is better as the two layers of polyester offer protection for the dye or material inside which helps protect it from fading. The film is also thicker, usually between 38 and 50 microns, which make it a little easier to handle. The only time this is not the case is for car window tint, 1 ply is usually easier to work with as it is thinner and easier to heat shrink (a process that involves heating the film so that it can be moulded to the contour of a compound curve such as a rear windscreen).