Pentair Pentek ECP Series cartridges are manufactured from a special formulation of resin-impregnated cellulose and polyester fibers. This unique blend provides higher wet strength than regular cellulose cartridges along with high flow rates and dirt-holding capacity while maintaining extremely low pressure drop. With a nominal 5 micron rating, the ECP5-BB reduces dirt, sand, silt, rust, and sediment particles to keep your water cleaner and help protect appliances, plumbing, and downstream filters. The media is pleated around a polypropylene core for added strength, the Big Blue cartridge uses molded endcaps with gaskets, and the overlap seam is sonically welded to reduce internal bypass. The design also delivers minimal unloading and media migration, and the white color-coded endcap identifies the 5 micron rating. This 10-inch Big Blue cartridge measures 10" x 4.5", contains about 18 square feet of media, and drops into 10-inch Big Blue and other heavy duty housings. Initial pressure drop is less than 1 psi at 20 gpm over a 40 to 125 degrees F range. This pack includes 8 cartridges; replace each one whenever you notice a drop in water pressure or water quality.