Fangrui Product Details 1. Doberman Se-0137 4 In 1 Household Anti-theft Door And Window Magnetic Spring Sensor Super Loud Simple Alarm Set 2. Simple Alarm, In The Alarm State, The Door Will Alarm When The Door Is Opened, And The Alarm Will Stop When The Door Is Closed. 3. The Sound Of 100 Decibels Is Enough For The Thief To Flee. 4. Use Electricity For A Long Time, Energy Saving And Environmental Protection. 5. The Back Comes With Eva Strong Adhesive, Easy To Install, Fast And Convenient. 6. When Installing, The Reed And The Main Unit Must Be On The Door And One Outside The Door. The Distance Between The Two Is Preferably 0.8mm. 7. Product Specifications: 8. Host Size: 50x38x20mm. 9. Power Supply Prevention: 3 Ag13 Button Batteries. 10. Alarm Volume: 100 Decibels. 11. Length Of Use: (new Battery) More Than One Year.