Four-level temperature control. One red light on: the temperature is about 45-50℃, the battery life is about 6 hours. Two red lights on: the temperature is about 50-60℃, the battery life is about 5 hours. Three red lights on: the temperature is about 60-70℃, the battery life is about 4 hours. Four red lights on: the temperature is about 65-70℃, the battery life is about 3 hours.