Mini Wireless Door & Window Contact Alarm & Chime Set of 2, Batteries Included, Louder Than 90db, Mounted By Double Adhesive Tape Operated by three 1.5VLR44 button cell batteries(Included) , On and Off Switch Residential use: Protects exterior door, sliding glass door,gun and medicine cabinets. Commercial use: Protects showcases and cash registers Magnetic sensor switch detects entry protecting you home or office whether you're in or out. Chime or alarm mode. High Quality Intrusion Alarm, Louder than 90 dB alarm scare off potential intruders . Inconspicuous and Wireless, Easily mounted by double adhesive tape to window or door, no tools required.