AquaRain is a gravity-fed ceramic cartridge filter system similar to the British Berkefeld, Berkey, Katadyn, Doulton or Pro Pur. Since a virus cannot be filtered out by any of these devices, we would never recommend them for use with surface water, only for well water or tap water. Beware of claims made by water filter companies with ceramic filters who make such claims! With a .3 micron rating the AquaRain filters down to about the smallest size possible for a gravity-fed system. AquaRain filters are made in the USA.