On some windows, mainly non-winding, there are black dots around the edge of the glass. This is called the dot matrix and is produced using a Teflon type material, which is factory fitted. When the film is applied it sticks to the dot matrix and not the glass, which traps air and water between the dots giving it the silver look. With some windows, it can’t be helped whereas others will evaporate and look fine. It all depends on the thickness of the dot matrix, which will vary depending on the make and model of the car.