NEDIS ALRMD20WT Door/Window alarm with magnetic sensor batteries included

Wireless magnetic door - window alarm, 85 dB.

The ultra slim window/door alarm is designed to trigger an alarm when a door or window is opened. With a simple switch on the side of the device so it can be turned on and off if necessary.
The slim profile makes it ideal for window or door mounting. The alarm is powered by 2 CR2032 batteries, which are included in the package, and its average life for normal use is one year. The alarm has an indicator light to alert you when the battery is low. Press the "Battery test" button on the front of the device to check the battery status. Its installation is easy thanks to the double-sided tape. Simply stick the alarm and magnetic sensor to the door or window and you're done.