Let's be blunt. According to the Center for Disease Control, debilitating diarrhea is the most common illness affecting U.S. citizens traveling abroad - with between 20-50% being afflicted each year! And it doesn't matter if it's tap water in your room, water from a running brook, or that inviting glass of cool water poured by tuxedoed waiters at a 4-star hotel in Hong Kong - the results are too often the same. Take SteriPen along, and you can quench your thirst without ruining your trip! Portable Purity - Just 6.1 long and 2.3 oz., SteriPen packs powerful UV purification into a compact instrument that's a breeze to use. No foul-tasting chemicals that may or may not work. Instead, SteriPen uses the same technology used by U.S. spring-water bottling plants to purify your water. Literally destroys the DNA in microbes, so they cannot reproduce (or cause illness!). A powerful, germicidal UV lamp comes on automatically when immersed in a glass of water. In just 48 seconds, SteriPen destroys over 99.99% of all dangerous waterborne bacteria, viruses and protozoa in 16 oz. of water - including E-coli, Dysentery; Cholera; Hepatitis; Influenza; Giardia Lamblia; Salmonella and dozens more! Also fits into the containers of the majority of bottled waters sold overseas - a good precaution. Equally effective in the wilderness, where deceptively clear babbling brooks temp thirsty hikers. But beware! Dangerous bacteria, viruses and protozoa can turn a walk in the woods into a nausea nightmare! Includes 2 non-rechargeable lithium CR123A batteries; single button selects 16 oz. or 32 oz. treatment; counter indicates when UV lamp must be replaced (after approx. 8,000 usages!). Includes protective cap and nylon carry case.