The Pentek ECP5-BB is a pleated cellulose polyester water filter designed with a special formulation of resin-impregnated cellulose and polyester fibers. They provide higher wet strength than regular cellulose cartridges with high flow rates and dirtholding capacity, while maintaining extremely low pressure drop. The filter media is pleated around a polypropylene core for added strength and the ends are immersed in a thermo-setting vinyl plastisol. Embedding and sealing each end of the pleat block in this fashion fuses 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. They are 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.