Katadyn® Vario water filter has a 2-mode design that lets you opt between fast filtration or extended lifetime of the primary filter (up to 500 gallons!). Vario features a 2-filter system; 1 is a 0.3-micron, pleated glassfiber filter used to remove waterborne bacteria and cysts. Secondary ceramic filter, engaged with a simple twist of the casing, is used to prefilter debris in dirty water away from primary filter. Keeping turbid water away from the primary filter effectively extends its usable life. Vario is also a high-output system, filtering up to 2 qt. per min. in "fast flow mode" (filtering clean water with ceramic filter disengaged). In "longer life mode" (ceramic filter engaged), unit produces 1 qt. per min. Replaceable carbon keeps water tasting fresh and reduces chemicals, toxins and odors through the life of the cartridge. Dual-piston technology minimizes the effort required to pump water through the system.