Pentek WPX50BB97P Big Blue String Wound Sediment Replacement Water Filter Cartridge Compatible With Culligan, Ametek, US Filter, Plymouth, Kleen Plus, American Plumber, Bruner & Many Other Brands. WPX50BB97P Big Blue 50 Micron Fibrillated Polypropylene String Wound Sediment Water Filter Replacement Cartridge. 10" long X 4 1/2" diameter. 8 per case, sold individually. #WPX50BB97P. The WPX-BB Series cartridges are constructed of fibrillated polypropylene wound on a polypropylene core. The fibrillated polypropylene should be used when pressures require minimization of extractables and/or fiber migration. These Are High Quality Sediment Water Filters. Order a case and save even more.