Crystal Quest Iron Replacement Filter Cartridge is manufactured with Eaglesorb Iron Removal Media. They are designed to provide an easy and effective method of reducing iron in water. Most ground water contains some iron which naturally leaches from rocks and soil. These cartridges help to greatly improve taste and eliminate the orange and brown stains often found in sinks, tubs, toilets and their plumbing fixtures when there is an excess amount of iron in the water supply. Cartridges should be backwashed to maximize capacity.