Pentair RFFE20-BB Big Blue Water Filter, 20-Inch, Whole House Radial Flow Iron Reduction Replacement Cartridge, 20 X 4.5, White. GREATLY IMPROVES TASTE by filtering up to 3 PPM of dissolved iron. PREVENT RUST STAINS on sinks, toilets and plumbing fixtures and prevent appliance damage. WHOLE HOUSE FILTERING on main water line, works great for well water. FITS ALL 20″ Big Blue Housing and can replace any 4.5″ x 20 Iron reducing filter. REPLACE EVERY 3 MONTHS for 3PPM reduction with a family of four. See image chart for more details. Material: Manganese Activated Zeolite. Product Dimensions: 4.5″D x 20″W x 4.5H. Item Weight: 3.08 Kilograms. External Testing Certification: NSF. Product Benefits: Removes Impurities. Item model number: RFFE20-BB. Size: Pack of 1. Style: 20″ x 4.5″. Item Package Quantity: 1. Number Of Pieces: 1. Cutting Diameter: 4.5 Inches. Assembled Diameter: 4.5 Inches.