Pentair ECP Series Cartridges are manufactured from a special formulation of resin-impregnated cellulose and polyester fibers. This unique blend of materials provides a higher wet strength than regular cellulose cartridges. It also provides high flow rates and dirt-holding capacity while maintaining extremely low pressure drop. The media is pleated around a polypropylene core for added strength. The pleated endcaps of the standard cartridges are immersed in a thermo-setting vinyl plastisol. The Big Blue cartridges have a molded endcap with gaskets. The pleated ends are sealed to the endcap with a thermoplastic adhesive. The overlap seam is sonically welded to reduce internal bypass, improving filtration efficiency. ECP Series Cartridge endcaps feature a color-coding system for easy identification of micron ratings: tan (1 micron), white (5 micron), blue (20 micron), and yellow (50 micron). KEEP YOUR WATER CLEAN and protect your appliances by removing dirt, sand, silt and particulates FITS ALL 10″ Big Blue housings or other 10″ heavy duty housings and can replace any 10″ x 4.5″ heavy duty sediment filter cartridge LONGER LIFE with 33% more dirt holding media than many competitors STRONGER than standard cellulose cartridges with a unique blend of resin-impregnated cellulose and polyester REPLACE EVERY 6 MONTHS or when you notice a drop in water pressure or quality. The cap is color-coded for easy replacement.