Multiple Brightness & Brake Sensing:Our taillight has 3 brightness modes to adapt to different environments. At the same time, when cycling brakes slow down, the tail light will remain on for 3 seconds to warn the vehicle behind, ensure personal safety, and give you a good cycling experienceDynamic Modes & Easy Install:Choose from 4 dynamic light modes: (1) Normal Flash, (2) Breathing Flash, (3) Fast Flash, (4) Steady On. Tailored for diverse riding conditions day and night. Effortlessly install with metal under-seat or rubber band seat post mounts. Fits road, mountain, cruiser, scooterExtended Battery Life & Intuitive Power Display:Stay powered during your rides with the 400mAh Li-ion battery. The built-in power indicator features four blue breathing lights, each indicating 25% battery capacity, ensuring you know when to rechargeFind Your Kindred Spirit:This bicycle tail light, while in motion, automatically syncs with nearby companions equipped with the same rear bike light, maintaining identical blinking patterns. (User-initiated double tap required for activation) Regardless of your group size, as long as everyone is using this light, you can maintain the same blink frequency, letting everyone know you're a unified team. It's the epitome of coolSmart Auto On/Off & IPX6 Waterproof: Experience intelligent functionality with our bike rear light. Equipped with Motion and Light Sensors, it automatically turns off after 30 seconds of inactivity. Once movement is detected or your bike is in motion, the light reignites (auto on/off applies to modes 1 and 2). For continuous daytime visibility, opt for modes 3 or 4 to bypass the Light Sensor (Brake sensing is active in all modes)