Only use genuine Multipure replacement filter cartridges. If you find one for less, it's a fake. The filter cartridge is the heart of every Multipure Drinking Water System, and has been NSF Certified. All replacement cartridges are made fresh weekly at the manufacturer, so when you buy one direct from the source, you are getting the freshest product with the latest technology. Filters that merely "fit" Multipure are not genuine and do not remove the same contaminants that a genuine Multipure cartridge does.