Birds navigate by using the earth’s magnetic field. Disrupt that field and they completely lose their sense of direction. Bird barrier’s magnetic system disturbs the magnetic field for a 20' radius-without batteries, electricity or costly operation! Holographic surface provides added deterrence. Completely safe for birds, people, pets and the environment. Hangs from any surface. Made from durable man-made materials and measures 4 1/2"W x 6"H.