Aries (AF-20-2215-BB) 20"x4.5" Big Blue 5 Lb. KDF-85-GAC FilterAries Filter Works AF 20 2215 BB 20"x4. 5" Big Blue KDF 85 GAC Filter Heavy duty specialty filter combining 5 pounds of KDF 85 media with granular activated carbon for iron, hydrogen sulfide, and chlorine removal in whole house applications KDF 85 Media Iron & HS Removal 20x4. 5 Big Blue 5 Lb Capacity The Aries AF 20 2215 BB addresses common well water problems with a dual media approach: KDF 85 alloy removes iron, hydrogen sulfide, and heavy metals