Sprite High Output Shower Filter Replacement Cartridge. *20 oz. KDF-55 and Chlorgon. *New clear housing allows peek at filtration media! *NSF Certified for 25,000 gallons This is an HOC high output replacement cartridge rated for 25,000 gallons. Most shower heads flow at a rate of 2.5 gallons per minute. That is equal to 10,000 shower minutes. Or, simply put, two people can take one 13.5 minute shower per day for 1 year. Additional showering will reduce the life of the filter, so replace accordingly.Fits: All HO Series, All HO2 Series, All HOB Series