The Kirsch Spring Pressure Rod Pair is for use inside a window frame. They need no brackets and are generally used for gathered curtains. They are made of steel with a durable white enamel finish with covered ends made of rubber to prevent scratching of your window frame. Adjusts to fit windows between 8″ and 16″ wide. Select from two sizes: 8 to 11 inches, or 11 to 16 inches.