Pentek ECP5-10 water filter cartridges have a special formulation of resin-impregnated cellulose and polyester fibers. The Pentek ECP5-10 water filters also provide high flow rates and dirt-holding capacity, while maintaining extremely low pressure drop. The Pentek ECP5-10 water filters provide higher wet strength than regular cellulose cartridges. The Pentek ECP5-10 water 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 Pentek ECP water filter cartridges contain more media surface area than most competitive cartridges. The standard 10" ECP cartridges contain six square feet of media, where most cartridges contain only 4.5 square feet. The Pentek ECP5-10 replacement filter cartridge 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.