Strauss Bicycle Solar Tail Light and Bicycle Speedometer, (Black/Red) Solar powered the solar bike light full charged needs 4 hours(sunlight) and work for 6-8 hours Solar power, energy saving, environment friendly with 3 modes of light, slow flash, quick flash, steady light Multi functions with auto sleep and wake-up its records speed in mph/kmph, riding time, distance, scan, maintenance alert Distance speed tracking and clear large display as the wonderful percent wireless sign showed This bicycle speedometer is waterproof and works great on rainy days as usual when riding