The Katadyn Exstream Virustat Replacement Water Bottle Filter Kit reduces particles, protozoa, bacteria, and viruses, The first stage reduces large particles and odors, The second filter made of glass-fiber reduces cysts, The third stage is a Virustat cartridge that kills bacteria and viruses with iodinated resin, The Katadyn Exstream XR Virustat Replacement Filter Kit includes: replacement filter for all three filtration stages, The Katadyn Exstream Virustat Water Bottle Filter is good for up to 26 Gallons or 125 refills (capacity depends on water quality), SKU: CWD706