iSpring FC25BX2 - NSF Certified High Capacity 4.5" x 20" Big Blue Whole House Water Filter CTO Carbon Block - Pack of 2 Made from high-quality coconut shell carbon and individually wrapped for freshness, tested by independent third-party to meet NSF/ANSI Standard Lower pressure drop, no release of carbon fines, great physical strength, highly porous, high adsorption, steady flow, highly uniform, and solid structure integrity Effective reduction of sediment, chlorine, and a high removal capacity of unpleasant odors, and tastes Length: 20 in., O.D. - 4.5 in., I.D.- 1 in. 1/4 in. fitting