This survival straw works immediately and is simple to use. Proven technology capable of 700 litres of natural tasting safe drinking water free of contaminants from any source. Light yet robust, the Web-tex surviva-pure system has built-in purification and post purification filtration that destroys and removes Cryptosporidium Giardia, Anthrax and many more harmful bacteria. Contains Web-tex Surviva-Pure purification system. Filter contains pre-filters and built in EPA purification medias that will outlast the life of the filter. Filter contains post-purification scrubbing system.