Aries FilterWorks AF-20-2125-BB 20" x 4.5" KDF-55 & Coconut Shell GAC Water Filter Cartridge - (2.5 lb) Reduces Chlorine, Heavy Metals, Scale & Microorganisms - Made in USAThe Aries FilterWorks AF 20 2125 BB combines 2. 5 pounds of KDF 55 redox media with acid washed coconut shell GAC in a 20" x 4. 5" double open end cartridge engineered for whole house and point of use chlorine, heavy metal, and scale reduction. This full flow design from ResinTech's Aries division delivers 50% more capacity than standard 2. 5" diameter filters while maintaining compatibility with Pentek, GE, Culligan, and most 20 inch Big Blue