3pcs Big Blue Water Filters-Sediment,Carbon & GAC+KDF 55 Block: 4.5"x20" Top Quality Replacement which fits most Big Blue 20" Whole House Systems. Includes: 1PCS Sediment Filter (5 Micron), 1PCS Carbon Block (5 Micron) & 1 GAC Carbon + KDF 55. Cartridges are designed for high-flow water filtration applications. Perfect for well water. Unique, wide cartridges are capable of filtering enough water for a house, apartment or office.