Genuine, OEM Whirlpool filter reduces contaminants to provide clean, fresh tasting water. Replace every 6 months for optimal performance. Used on refrigerators that do not have built-in water filters. This filter is installed in the water line, behind the refrigerator. NSF 42 Certified coconut shell activated carbon filter medium reduces chlorine taste ad odor, rust, sediment, and other impurities.4378411RB (AP4415498) replaces 11-200, 14200105, 1603265, 18001001, 18001001A, 4210359, 4210508, 4210573, 4378411, 4378411P, 4378411RP, 4378442, 8004, AH2351893, EA2351893, PS2351893, R0183114, R1831-14, WF260, WF270.