Aries (AF-20-3310) 20"x2.5" (1 Lb) Phoshphate-GAC Carbon FilterAries Filter Works Aries AF 20 3310 20"x2. 5" Phosphate GAC Carbon Filter 1 lb phosphate crystal cartridge with granular activated carbon for scale prevention, corrosion control, and taste improvement in whole house and commercial applications NSF 61 Listed Phosphate FDA Grade Materials 20x2. 5 Standard Size Dual Action Treatment The Aries AF 20 3310 combines phosphate crystals with granular activated carbon to address both mineral scaling and water