... stage is 5.0 micron PP filter . 2. The second stage is Milfunction+active carbon ro water system 400G pumpless tankless stainless ... first stage is 5.0 micron PP filter .filtering s, rust, mud, sediment, etc. in water.2. The second stage is Milfunction ... osmosis membrane filtering germ, virus, corpuscule, other solute chemical from tap water processing. household stainless steel RO water filter system