Pentek ECP1-20BB Pleated Cellulose Polyester Filter Cartridge, 20" x 4-1/2", 1 Micron Reduces sand, dirt, silt, rust, and scale particles in residential and commercial water Nominal filtration rating of 1 micron Resin-impregnated cellulose and polyester media pleated around a polypropylene core for strength Initial pressure drop of less than 1 psi at a flow rate of 20 gpm Temperature range of 40 to 125 degrees F (4.4 to 51.7 degrees C)