1. 4 in 1 Multi-Function --- General Alarm, Constant Alarm, Closing-door Alert (Time Delay), Doorbell2. Batteried by 2pcs AAA batteries ( not included ).3. Self-Adhesive, easy to install and operate.4. 108 dB Loud Alarm can effectively prevent intruder entering through your door/window.4 in 1 Multi-Function:1.General alarm mode It alarms when doors/ are open; Stops when they are closed.2. Constant Alarm Mode It alarms at least when triggered.3. Time Delay Mode It sounds "di-di-di" when doors/ opened 15 seconds later (Can set the delay time 3/15/30/60 seconds, the factory default is 15s). This is perfect for freezers or refrigerators.Material: ABScolour: WhitePackage Contents:1 x Door/window Alarm1 x Magnetic Stripe Double Sided Sticker User ManualOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.