Window Door Entry Wireless Alarm System Pack Of 5

It can also be used to alert you of an opening of a sliding glass door, door, window, locker, Gun cabinet almost anything!
Easily mounted by adhesive tape to window or door.
Magnetic sensor switch detects entry protecting your home or office whether you are in or out
Warning door, window sticker is supplied free in package. Operated by 3pcs.1.5VLR44 button cell
Batteries included in the package.

Dimension:
12.5cm x 9cm x 2.5cm (retail packing)

Instruction for use:
use the double-sided adhesive tape to fix the main unit at the door/window frame with the arrow aligning with the reference of the main unit.
Test the setup by switching the system's switch to "ON" position of the main unit and see whether the alarm can be triggered by opening the door or window.