Using ultraviolet (UV) light to purify water, the SteriPEN makes drinking water safe in seconds by killing harmful viruses, bacteria and protozoa like Giardia and Cryptosporidium. Just fill a container with clear water, push a button, dip it in and stir. In just 90 seconds, you will have 32 oz. of clean-tasting water that is safe to drink. It is perfect for people traveling to "at risk" water countries and for peace of mind in water emergencies anywhere. At just 4.6 ounces, it fits in the palm of your hand. Runs on two lithium 3V batteries (not included). Includes carrying case.