About this product: Hard metal shell, not easy to deform, the sound reaches 100dB, the maximum range is 600-800 square meters, and it is farther and safer. Pure copper electromagnetic coil with discontinuity and no electromagnetic interference, strong grip, stable operation and long service life. The surface is coated with electroplating technology which makes the material more anti-corrosive and less prone to rust and corrosion. Wired portable power supply, easy to install, can be mounted on the wall, ceiling or other methods. Product Specifications: Condition: Brand . Colour: red. Material: Metal. Size: 4 inches (100mm). Power mode: external. Voltage: 220V. Alarm volume: 100db. Surface treatment: electroplating. Package list: 1 * Fire Alarm Buzzer.