Easy installation with adhesive tape, just stick on and go. Attach the main unit and magnet unit on door/window and door/window frame, keeping them in horizontal alignment, then turn on the switch, when the two parts separate the alarm will generate loud alarm sound to inform there is a intruder. Work as an anti-theft alarm, alarm volume up to 80dB. Can be used in doors, windows, cabinets, drawers to detect intruders. Compact size and cheap price, a perfect kit for your home and office security system. Specification: Material: PP Main Unit Size: Approx. 9.2x3x2cm/3.62x1.18x0.79 inch Magnet Unit Size: Approx.5x1.5x1cm/1.97x0.59x0.39 inch Power: 3 piece AAA battery (not Included) Quantity: 100 Package Includes: 100 Pieces Door Window Alarms Note: Since the size above is measured by hand, the size of the actual item could be slightly different from the size above. Due to the lighting effects, monitor settings, etc. There could be some slight difference in the color tone of the pictures and the actual item.