Not just a Filter Cartridge. Pleatco is a complete Filtration System! Pleatco Free Flow Cores, REEMAY Filtration Fabric, Antimicrobial Endcaps and Superbond Bands make the Pleatco product compass to differentiate the key components of why Pleatco Filter Cartridges are the best products on the market. Pleatco Free Flow cores allow for the free flow of water through the filtration fabric increasing the effectiveness of the filter.