Feature 1Voltage spike and surge conservation and anti dust, vibration, moisture. 2Produces a powerful beeping sound that is 112dB,helps warn when the vehicle is backing-up. 3Designed to work on 12-24 volt DC vehicles, automatically adjust to a voltage range of 12-24 volt engineering vehicle. 4Made from premium materials to ensure durability and longevity,perfectly work in a variety of temperature environments. Features: Voltage spike and surge conservation and anti dust, vibration, moisture. Produces a powerful beeping sound that is 112dB,helps warn when the vehicle is backing-up. Designed to work on 12-24 volt DC vehicles, automatically adjust to a voltage range of 12-24 volt engineering vehicle. Made from premium materials to ensure durability and longevity,perfectly work in a variety of temperature environments. Specifications: Power: 30W Color: Black Decibel: 112dB Material: Plastic Current: 2.0-2.5A Voltage: 12V-24V DC Package Weight: 730g/25.7oz Package Size: 13.5*10*8.5cm/5.3*3.9*3.3in Note: 2 positive poles and 1 negative pole. Connect the positive and negative poles respectively, which can make two kinds of sounds. Connect two positive electrodes and one negative electrode at the same time to make third kind of sound. Package List: 1* Reverse Horn 3* Connecting Cable Package List1* Reverse Horn 3* Connecting Cable