Self-Powered Electromagnetic Induction This bicycle taillight operates without the need for charging, using a built-in 50mAh lithium battery powered by electromagnetic induction. The light automatically activates when the wheel rotates and shuts off after the bicycle stops for a short period.Speed-Responsive Flashing Mode The taillight adjusts its flashing speed based on the bicycles movement. The faster the ride, the more frequent the flashes, enhancing visibility. Once the bicycle stops, the light continues flashing for 30-60 seconds before turning off.High Visibility with Optical Lens Cover The circular optical lens improves light transmission through the red LED, increasing visibility from a greater distance. This enhances recognition on the road, providing a clear signal for surrounding traffic.Easy Installation Without Battery Replacement This light is designed for hassle-free mounting on seat posts with a diameter of 20-28mm. It does not require battery changes or USB charging, ensuring continuous operation without maintenance concerns.Waterproof and Non-Contact Power Generation Featuring a water-resistant design, this taillight can withstand splashes and light rain. The non-contact magnetic induction system generates power without friction against the wheel hub, minimizing wear and optimizing efficiency.