SteriPEN Emergency Handheld Water Purifier harnesses the power of ultraviolet (UV) light to purify drinking water. Water bottling plants and cities purify water using UV light. Now you can hold this purifying power in your hand. Purify 16 ounces of water in only 48 seconds (or 90 seconds for 32 ounces). SteriPEN Emergency Handheld Water Purifier eliminates over 99.9% of bacteria, viruses and protozoa such as giardia and cryptosporidium.