Aries (AF-20-2214-BB) 20" x 4.5" (4 lb) KDF-85-GAC FilterAries Filter Works Aries AF 20 2214 BB 20" x 4. 5" KDF 85 GAC Filter Industrial grade filtration for iron, hydrogen sulfide, and bacterial control in whole house and commercial well water applications 4 lb KDF 85 Media 20" x 4. 5" Big Blue Coconut Shell GAC WHY IT WORKS Redox chemistry meets activated carbon for complete well water treatment KDF 85 Redox Process Four pounds of KDF 85 media removes hydrogen sulfide and reduces iron through oxidation