Aries (AF-20-2085-BB) 20"x4.5" Big Blue KDF-85 FilterAries Filter Works Specialty Filtration Aries AF 20 2085 BB 20"x4. 5" Big Blue KDF 85 Filter High capacity redox media filter for hydrogen sulfide and iron removal in whole house applications KDF 85 redox media Removes hydrogen sulfide Reduces iron and heavy metals Bacteriostatic protection The AF 20 2085 BB combines KDF 85 redox media with ResinTech coconut shell granular activated carbon (GAC) to address common well water issues including hydrogen