This new with the box post carbon water filter is for sale, since it was purchased by mistake since my machine only has 3 filters and no 4th one. It is a block post coconut carbon filter designed for domestic and commercial RO systems (reverse osmosis). This white cartridge has a twist and lock seal and is rated for a maximum flow of 3.6L/min. It has a service life of 3500L and operates at pressures between 0.1Mpa and 0.4Mpa.