SMART BRAKE BIKE TAIL LIGHT: Easy to set. Double click the button quickly then enter the smart brake mode. And double click the button quickly again will exit this mode. More details can see picture 2 or description MULTIFUNCTIONAL SAFETY LIGHT: Easy to install. Lightweight and durable bike tail light that can be mounted on all bikes, children's bike, adult bicycle, handlebars, seat posts, dog collars or anywhere. It also can be used as helmet lights, backpack lights, warning lights and more SET YOUR OWN LIGHT MODES: 5 light mode options: Strobe(9 hours), Slow Strobe(56 hours), Meteor Flash(14 hours), Windmill Flash(17 hours), Breathing Flash(8 hours). You can switch different modes according to your needs and different occasions to get the best lighting experience WATERPROOF NO BATTERIES REQUIRED: Built in USB charge port for this bike rear light (USB cable included). The taillight is made of IPX4 rated water resistant material to ensure a safe use in heavy rain WARRANTY: Any problem can contact with us, and we will try to solve it within 26 hours.