12 HOURS LONG STANDBY TIME: USB rechargeable batteries 2 hours charging, 12 hours working.Unlike other armband light needs to be charged after running every time.Extended-capacity battery will save your time and money. 200M DISTANCE WARNING AT NIGHT:Longer visual range and higher brightness ensure more safety when running,jogging ,walking ,cycling,hiking,walk dog and other exercise. 11-13 ADJUSTABLE SIZE: Fit on both adult and children,wearable for the wrist, ankle, arm and leg. A warm runner accessories for women and men. WIDELY APPLICABLE:Widely used for rain, fog, dark,cloudy,night and other low visibility conditions,increasing visibility and safety during early morning night sports and outdoor activities. 4 Models: fast flashing, slow flashing, continuous bright and off. You can switch freely according to different the weather and time.