Worldoor&reg; Door/Window Entry Alarm with Magnetic Sensor, Wireless Home Doors Windows Security Entry Alarm System - EASY to install FREE BATTIRES!! Pack of 2 Easy tool-free installation to window or door; Mounted using double-sided adhesive tape (included) Magnetic sensor switch detects entry protecting home or office Three 1.5V button cell batteries, INCLUDED Pack of 2 sensors for two windows or doors 90 DP plus @ 3 ft. sound level