The Alter Ego filtration technology provides the greatest reduction per contaminant. The Outdoor filter cartridge removes everything up to 4 log (99.99%) from chlorine and heavy metals to agricultural run-off and industrial waste, including giardia and cryptosporidium. Laboratory tested and field-proven over ten years, Alter Ego water filters can transform a questionable water source into clean-tasting, contaminant-free water. The outdoor filter is perfect to fulfill all of your urban and backcountry needs in the northern hemisphere where viruses and water-born pathogens are not a problem.