110 - 120dB loud enough to attract and warn walkers. 3 switchable sound modes. Charges any device with a USB port. With flexible rubber band, easy to install or release, no tools required. Mini size and light weight, save space for handlebar. Note : The data are all measured manually, please allow 1-3cm error due to differences in light and display, there may be color differences, please refer to the actual item received.