The Pentek WPX25BB97P is a nominal 25 micron fibrillated polypropylene String-Wound sediment filter. These water filter cartridges are constructed of fibrillated polypropylene wound on a polypropylene core. They should be used when pressures require minimization of extractables andor fiber migration. The WPX25BB97P water filters reduce sediment, sand, and silt.