Zen Water Systems UF-F Ultra Filtration Membrane Filter Membrane or "micro-tubes" with pores that measure 0.1 to 0.2 micron in size An alternative to Zen Water Micro-Ceramic Filter No maintenance. Discard at end of useful life Life of filter is approximately 1 year or 1,000 gallons, or until pores are clogged and water unable to pass through Be sure to use only genuine Zen Water replacement ultra-filtration membrane filter for optimal performance