Wireless Security Sensor Set for $5.22

At only 2 1/2 inches long this economical alarm inconspicuously protects your home from intruders. This unit uses a magnetic sensor to detect the opening of a protected door or window. A 90 dB alarm will then alert you to an attempted entry and scare off potential intruders. The owner may open the window or other protected object, without setting off the alarm by switching the on/off switch to the off position.