This penlight is for medical use. Penlight works great as an emergency light. Attach it to your pocket with the handy pocket clip when you're on the go. At just similar size like pens, this handy unit won't tug too hard on your pocket even when you're jogging down the hall. Powered by AAA alkaline batteries , the light burns for up to 60 hours. A tempered aircraft-aluminum body with anodized finish means years of reliable use.