Used by the military during Katrina. Makes over 3 Liters of clean drinking water a day for 3 days. Makes virtually any water drinkable even muddy water.The filter itself has a microscopic pore size of 3 to 5 angstrom; 100 times smaller than the smallest pathogens and 200 times finer filtration than competitive filters. The system this filter uses is forward osmosis. Meet all EPA standards.