Using the advanced hollow fiber technology of MSRs award-winning Guardian™ Pump, this gravity-powered sibling features two-stage purification: a .02 micron hollow fibre membrane that removes viruses, bacteria, protozoa, and particulate; and activated carbon to reduce chemicals, tastes and odours. Both the original Guardian™ Pump and new Guardian™ Gravity Purifier stand out because they remove not just bacteria and protozoa, but the tiniest waterborne pathogensvirusesas well, which are of greater concern as more and more people visit the backcountry with less regard for their waste. With the Guardian™ Gravity Purifier you get this high level of protection in a high-volume, versatile, convenient system that serves all of your daily water needs quickly and easily.