Pentair Pentek WS Series Cartridges are designed to allow optimal contact between water and resin surfaces, ensuring maximum ion exchange. The internal expansion pad minimizes channeling, while the post-filter eliminates any potential for bypass. Designed for low water usage, these units will easily deliver softened product water through the use of a sodium based, non-solvent rinsed softening resin. The cartridge style design provides a convenient solution for delivering softened water to protect sensitive water delivery equipment. Water Softening Cartridges provide superior performance and outstanding protection for medical equipment, coffee and espresso appliances, low volume beverage and commercial food service machines.