Harmsco® Polyester-Plus™ 801 Series filter cartridges are made of highly efficient pleated polyester filter media. Polyester-Plus filters have the industry's largest surface area and fit non-Harmsco cartridge filters. The thermally-bonded endcaps ensure better sealing and are color-coded for easy micron rating determination. Harmsco filters are made of FDA approved materials and are NSF 61 certified.