The top dog of gravity powered purification filters, our primary filter (NF7) show test results that meet or exceeds all of the United States EPA standards needed to be considered a water purifier. Tested using GTW-3 quality it removed greater than 99.9999% of bacteria, 99.99% of cysts and 99.99% of virus. It has a production rate of up to 6-8 gallons per day. The filter (NF7) is differentiated from our sub micron filter (RF05-7) by blue end caps. The installation via a female to male thread assures a Surefit which minimizes the chance of bypass.