KEWAYO Bicycle Horn and Alarm Cycling Bike Alert Bells Ring Loud Electric Siren Mounting-Pipe Diameter: Approx. 2.5cm; Power Supply: 4 X AG13 Button Battery (includes in Package) Electron Loud Alarm: Sound likes chirp "chirp", more like a siren. Good performance of 90 dB sound,loud enough to attract attention and warn the walkers. Anti-theft Alert: When the horn is in the surveillance state, if the bicycle is vibrated, it will alarm with loud sound for 15 seconds. It is still in the surveillance state after first alarm. If the bicycle shakes again, a further 15 seconds alarms will follows. Password Security Surveillance: Once the security surveillance mode is setted, it won't withdraw until inputted the password. Simple One Key Control: Just press the button, the horn will give sound to reminder. And the control cable is about 14.5cm; Waterproof: The button is make of waterproof silicon material, it is safety to ride in a rainy day, but don't put