The Katadyn ViruStat Replacement Cartridge is designed to be used with the Katadyn My Bottle and Exstream personal water purification systems. It delivers 26 gallons (100 liters) of pure water, which can provide an entire month's worth (gallon a day) of microbe-free water for an extended trip or expedition.ViruStat water cartridges are EPA registered and remove over 99.9% of waterborne cysts and protozoa like Giardia and Cryptosporidium. It also kills over 99.9999% of waterborne bacteria and 99.99% of waterborne viruses. Essential for extended travel in regions with questionable water quality. Includes cyst filter and prefilter. Made in Switzerland.