RFC-20BB Whole House Filter Replacement Cartridge by Tier1The RFC 20BB Whole House Filter Replacement Cartridge by Tier1 provides a large surface area, which increases filtration effectiveness. This greater surface area in turn allows a high flow rate. This filter will last you up to 6 months, or every 100,000 gallons which equates to 4 gallons per minute, whichever comes first. This typically evens out to only 2 3 filter changes per year. The Tier1 RFC 20BB does an exceptional job of taking out chlorine