1/2/4Pcs Magnetic Wireless Loud Burglar Intruder Door Window Home Security Safety Sensor Alarm Features ltra-thin design, the back of the product adopts a high-viscosity back sticker, which can be installed on any door or window. High-precision materials, never false alarms. When the distance between the host and the magnetic strip exceeds 10mm, an alarm will be issued immediately. Low voltage reminder to remind you to replace the battery in time to protect the safety of you and your family at all times. The host and the magnetic strip are respectively attached to the door panel and the door frame. Turn on the toggle switch on the left side of the main unit, the door will alarm when the door is opened, and the switch can be turned off when the alarm is not required. Remind you immediately when someone come in. Prevent theft when no one at home, and the loud alarm will scare the thief so that you can sleep well at night without worrying about the intruders Package Include:1Pc/2Pcs/4Pcs*Door Sensor (depend on your choice) Note: Due to different personal measurement methods, there will be an error of 2-4 cm, please understand Thanks for your support