MSR Guardian Water Purifier

The Guardian was developed over 6 years in response to the U.S. military's request for a product that would protect Service Members from waterborne illness anywhere on earth.  It filters out protozoa, bacteria, and particulate but also purifies the water against viruses - something almost no filters can do because viruses are so tiny.  It does this by using advanced medical grade fibers which block viruses, unlike conventional hollow fibers.  These fibers can also withstand freezing and minor impacts.

Another great feature of the Guardian is that it self cleans.  On every stroke, 10% of the water is used to flush contaminants in the filter back into the source.  There is no longer any need to backflush or scrub your cartridge, and the fast flow rate is maintained.

This fantastic filter will last years and years due to a very long cartridge life.  It's also really fast: you can pump 2.5 litres per minute!

Effective against:  protozoa, bacteria, viruses, particulate 
Weight: 490 g 
Filter matrix: hollowfiber 
Flow (L/min):  2.5
Cartridge life (L):  10,000+