Replacement filter for: AO Smith Undersink Water Filter (AO-MF-B) - NSF certified to standard 42 for chlorine taste and odor. Use only certified, genuine A. O. Smith replacement filters for continued contaminant removal and system performance. Single stage water filtration from your existing faucet - Reduces chlorine taste and odor. No water is wasted, and nothing is added to your water during the filtration process. Filter lasts 6 months with an annual replacement cost of $40 or less - Includes one filter replacement cartridge.