GENSSI Backup Warning Alarm 102dB Beeper Tone Construction Truck Heavy Vehicle (4 Inches 102DB 12V-24V) Universal warning tone at up to 102DB to warn others when backing up your vehicle 12V-24V DC power source; Preferably your reverse backup bulb wire Stainless steel power and ground connectionterminals; Waterproof housing with epoxy embedded electronics Conforms to SAE J994 safety standards; Reverse polarity protected Size: About 4 inches (Width) x 3 inches (Height) x &lt;2 inches (Depth) (Pack of 1)