Having clean drinking water is critical when you're on backcountry adventures. Originally designed for the military, the Guardian water purifier removes bacteria, viruses and many other impurities so you can stay hydrated without worry. Patent-pending self-cleaning system cleans with each stroke; no need to backflush or clean filter. Rugged design stands up to heavy use and extreme environments. Purifies 2.5 liters per minute from nearly any water source and treats up to 10,000 liters. The only hollow fiber purifier on the market that can withstand freezing temperatures. Drop tested from 6'onto concrete. Meets NSF protocol P248, the testing standard used by the U.S. military for removing viruses. Also removes protozoa, bacteria and sediment. Made in the USA, components USA and imported.