Water purifiers are not just for backpacking. In fact, one may save your trip overseas. The primary cause of illness to travelers, whether a one-week jaunt or an extended Walkabout, is gastrointestinal distress. Even what seemed the safest trip can be ruined by illness. Usually it's the water. Moreover, countries with "safe" water supplies can contain unfamiliar bacteria that cause diarrhea. And don't rely on bottled water -- you have no way to know its purity. The SteriPEN Classic is a portable water purifier that uses ultraviolet (UV) light to destroy waterborne microbes. Includes 40x40 micron screen Pre-Filter to remove particulates from the water. The Pre-Filter is designed to be stored directly on a wide mouth bottle. Also ships with neoprene carry case and user guide. Requires four AA batteries. (Lithium recommended.) 6.4 ounces. 7.6 x 1.5 x 1.5 inches. Output 32 oz. per 90 seconds.