Baleen Filters AK-90031 Pool Filter Perfect replacement for: unicel 4ch-22 Perfect replacement for: pleatco pff25p4 Perfect replacement for: filbur fc-2399 Pre-Filters allow for quicker water balancing with fewer chemicals. Washing a filter will extend its life &amp; clean filters use less energy. The Jet Brush makes this quick and easy. Scum Magnets prevent scum andoil from making it to the filter for fewercleanings.