Replacement Ultra Filtration UF membrane for the ISPRING #CU-A4 Ultrafiltration Water Filtration System which utilizes State-of-the-art UF Hollow Fiber Technology, the same technology in personal water filters, which removes 7 log (99.99999%) of all bacteria and 6 log (99.9999%) of all protozoa. Its certified 0.1 micron (comparing to 0.2 micron in Watt UF3) absolute filter removes bacteria and protozoa at a higher rate than accepted EPA guidelines. It is estimated that VOCs (volatile organic chemicals) are present in one-fifth of the nation's water supplies. These contaminants can enter ground water from a variety of sources, including herbicide and pesticide runoff, gasoline or oil spills, leaking underground fuel tanks, disinfection byproducts, septic system cleaners, and chemicals used in the dry cleaning industry. The CU-A4 keeps you safe from these and other VOCs with its 4-stage filtration.