The Pentek / Ametek WP5BB20P String Wound PolyPropylene Filter is the affordable solution for reducing sand dirt rust scale and sediment particles from your water. 355223-43.This filter is constructed of durable polypropylene string that is wound tightly around a solid polypropylene core for maximum efficiency and filtration.The WP5BB20P fits the Culligan / Ametek / Pentek and other brand 20 housings. Filter life depends on water quality and usage. If you see a significant drop in pressure you should change your cartridge.