Cartridge filters are rated in microns to signify what level of SS they are able to filter out. The sediment cartridges can filter SS from 20 micron to as low as 0.5 micron. Specialist cartridge filters can be used to filter even more SS to as low as 0.2 micron.  The filters are usually built with a gradual decrease of filtration efficiency such as 5 micron – 1 micron –  0.5 micron if required.