This compact, attractive MAGNETIC DOOR ALARM uses magnetic affinity to initiate its 110 decibel siren. The base of the alarm is bolted to door or window frame, the actuator is connected to the window or door. The alarm is activated by opening the door or window. Great for any door or window, particularly those hard to protect sliding glass doors. Requires three lithium button cell batteries (included). This pricing is available ONLINE ONLY. Standard retail or in-store price is much higher.