AP420 (5527407/55274-07) Hot Water Protector/Scale Inhibitor Alternative Replacement Water Filter Cartridge by KleenWater 3M Aqua-Pure Hot Water Protector and Scale Inhibitor Alternative Water Filter by KleenWater Low Cost / High Quality Replacement Alternative Cartridge Compatible Repleacement for Selecto Scientific 101-260 ScaleOUT Alternative Cartridge for GE, 3M Aqua-Pure, Pentek, American Plumbe and Other Popular Filters Protects Hot Water Heaters From Corrosion and Hardness