The Pentek ECP20-BB is a Pleated Cellulose Polyester Water Filter Cartridge that has a special formulation of resin-impregnated cellulose and polyester fibers. The Pentek ECP20-BB water filters provide higher wet strength than regular cellulose cartridges and high flow rates and dirt holding capacity, while maintaining extremely low pressure drop. The ECP20-BB replacement filter cartridge has minimal unloading and media migration. It is pleated around a polypropylene core for added strength and the ends are immersed in a thermo-setting vinyl plastisol which embeds and seals each end of the pleat block fuseing the components together forming a unitized end cap and gasket. The ECP water filter cartridges contain more media surface area than most competitive cartridges. The 10" Big Blue ECP cartridges contain 18 square feet of media. The Pentek ECP20-BB replacement filter cartridge is recommended for chlorinated water supplies. It is not recommended for non-chlorinated water supplies. Cellulose may start to break down if there is bacteria present in well water or other non-chlorinated water supplies.