You can use polarizers to look at the car window in the sun. There will be an aura like an oil film. 2. Install it on the rear window to see the color. Dark colors, especially dark ones, are painted %90. It is the privacy glass of other high-end cars, but most of the privacy glass is only installed on the rear window, and the front row may block the view. Look at the edge of the window. No matter how good the film is, there will be a little gap at the edge of the glass. 3. Scratch with your nails. Scratch with your nails. You can see if there are any movies. Glass is harder than film and leaves no trace. Look at the trademark. Many major manufacturers have logos on their films, but these logos can also be washed off with alcohol.