The Solar Therm Digital Thermometer is powered by solar cells and never needs a battery. Use this instant thermometer to take body temperature by mouth (oral), under the arm (axillary) or rectally. This solar digital thermometer when fully charged will work for 72 hours without light. Easy to recharge by placing the thermometer in sunlight or room light. Fast, instant thermometer measures temperature in as little as 9 seconds. The Solar Therm Speed thermometer beeps when ready, has a flexible tip for comfort, a JUMBO easy-to-read display and automatic shut-off. Recommended by a leading Women's Magazine. Sold Individually.