CRYSTAL QUEST 2-7/8" x 9-3/4" UF Membrane Filter Cartridge Ultrafiltration (UF) is an important purification technology used for the production of high-purity water. UF is effective for the removal of colloids, proteins, bacteria, viruses, parasites protozoa and pyrogens,  (e.g., gram-negative bacterial endotoxins), and other organic molecules larger than .01 Micron size and most other water contaminations known today. Also removes pesticides and herbicides, as well as the hardness in water and salts.