Their working principles are basically the same, except that the precision of the reverse osmosis membrane is better than that of ultrafiltration. Reverse osmosis membranes are generally below 0.001um, and ultrafiltration membranes are generally between 0.005~1um. Reverse osmosis is used to make pure water without any impurities, bacteria, or ions. The conductivity is basically close to 0. Ultrafiltration removes impurities and bacteria. Preserving a certain amount of ions is beneficial to the human body. It is specially used for making mineral water.