Principle of use: The alarm is installed on the door or window. If a thief wants to open the door or window, the alarm will sound immediately. The alarm uses magnetic induction control technology and has a long service life. Easy to install: use self-adhesive paste, no need for screws to install, just paste it and use it. Does not damage household items. More than 120 decibels alarm sound, protect your home. Sensitive alarm sensor, the alarm can be triggered by moving 1 cm. Use 3M double-sided tape for easy installation. Safe and convenient, easy to operate. Five core capabilities guaranteed Easy to install Can be installed in any opening and closing position Super sensitive, more than 1cm error can trigger an alarm Quality assurance, escort your home at any time Specifications: Power supply: 3*button batteries. Type: 4/8/16 pieces. Dimensions: 6.2x 4 cm. Package Quantity: 1 piece