Pentek WPX25BB97P String-Wound Polypropylene Filter Cartridge, 10" x 4.5", 25 Microns Reduces sand, silt, scale, and rust particles in residential and municipal drinking water and industrial fluid applications Nominal filtration rating of 25 microns Fibrillated polypropylene cord wound on a polypropylene core for strength and minimum extractables Initial pressure drop of 10 psi at a flow rate of 20 gpm Temperature range of 40 to 165 degrees F (4.4 to 74 degrees C).