The Birds Choice -The Great Hang Up Super Strong Window Hook for Bird Feeders has a lifetime durability.It holds up to 3 pounds, is made up of super strong polycarbonate. It can be mounted with hook in up or down position. To use : clean window glass throughly, then soak suction cups for two minutes in warm water. Press cups to reverse cups, then stick to window by pushing twice, releasing trapped air. Check occasionally to make sits secure.