2Pc Blue Super Loud Compact Electric Blast Tone Horn For Car/Truck/Suv 12V P4 for BMW X5 This is for a set of two (2)horns for 12V systems. These horns use a standard blade connector on the back. Rated at 118dB, these horns are nearly 7X LOUDER than a stock horn (@ 96dB) Each horn has a diameter of 123mm (4.8").