This is the bicycle speaker that records and plays any message to warn others of your presence. The device announces "On your left" or any verbal warning with the touch of a button, proclaiming your approach more effectively than a bell and without taxing your vocal chords. The unit holds up to a 20-second recording and the built-in 44mm speaker plays messages at 80 decibels (about as loud as a vacuum cleaner) to ensure your warning is audible over ambient noise. It can also play a traditional bicycle bell sound. Mounts to handlebars with the included clamp. Includes three LR44 batteries. 2 3/4" L x 2 1/4' W. (2 1/3 oz.)