Shelco (3) 2.5 x 10", 1-Micron String Wound Sediment FilterUse Shelco string wound filter as the first filter in the NanoCeram POU 3 under counter unit. These are gradient density for longer life melt blown polypropylene sediment pre filters. There are three layers of filtration, outer layer is 20 micron, second layer is 5 micron and the inner layer is 1 micron. NSF component, shrink wrapped for purity with the micron rating molded into the cartridge. This price includes 3 pre filters.