Good Waterproof Effect-The bicycle taillight is made of high quality plastic material, very waterproof. The taillights can withstand all bad weather conditions and riding in the rain is safe and worry-free. It also has a low battery reminder function.6 Flashing Modes-The bicycle taillight has 6 dimming modes, which provide extremely bright illumination on the 220 rear side, which is easier to find and greatly improves safety.Suitable Size-The suitable seatpost size for bicycle taillights is: 25-27mm / 0.98-1.06in. Use a screwdriver to quickly complete the installation and disassembly, simple and convenient. The taillights can be firmly fixed on the frame without worrying about loosening while driving.Battery Powered-The bicycle tail light can be powered by 2 AAA batteries, waterproof and shockproof, especially suitable for cross-country bikes and friends who often ride at night. (Note that this model does not contain batteries, batteries need to be purchased separately)Multifunction-Bicycle taillights can be used not only on bicycles, but also on helmets, strollers, backpacks and pet collars. Outside, it can be inserted on the backpack, mounted on the shelf, on the arm and other security warning places, the effect is very ideal.