The Water Softener Cartridges, utilizing a dark cation bead resin are designed to remove dissolved mineral hardness such as calcium and magnesium. These hardness minerals are typically the primary cause of scaling in pipes and water using appliances. Use a compensated hardness calculation that accounts for all mineral hardness of the influent supply to more accurately determine the gallon capacity of these cartridges. 10 Micron Nominal Rating Fits Most 20" Standard Housings Temperature Range: 40 F to 100 F Pressure Range: 25 PSI to 100 PSI