IMPORTANT: I tried these several times on a window and glass frame before shooting this video. HOWEVER after leaving them out overnight NOT on a window, they WOULD NOT stick to the surface. I am not sure if it was dust or if this will happen when they are on a window. Just use a little removable dry adhesive on the back if this happens to you. They are light and a little will stick them right on your window. The adhesive will not harm your window at all and can be removed after the season is over.