[4 Light Modes]: Choose from 4 modes: (1) Slow Red Flash: 3 seconds on when braking during the day, flashing + brake light + 30-second on/off at night; (2) Breathing Flash: Same as above; (3) Fast Flash: Continuous flashing + brake light day and night; (4) Steady On: Constant light. [ Brake Sensing & Auto On/Off]: The tail light activates when braking to alert others, ensuring safety at night. It features motion and light sensors, automatically turning off after 30 seconds of no movement and turning back on when motion is detected. Use modes 3 and 4 to bypass the light sensor. [ USB Rechargeable & Long Battery Life]: Built-in 260mAh lithium battery with TYPE-C charging, compatible with USB devices. Charging takes 2 hours, with a runtime of 7 to 16 hours. [ IPX6 Waterproof & Durable]: Rated IPX6 for heavy rain use, made from high-quality ABS + PC material, lightweight at 19 grams. [Easy Installation]: Includes saddle and seat post brackets for versatile mounting. No tools needed, easily removable for portability and theft prevention.