Four Black Berkey Filters (BF2) & Four Berkey Fluoride Filters (PF2); Black Berkey replacement filters will fit the following systems: Berkey Light, Big Berkey, Royal Berkey, Imperial Berkey, Crown Berkey, Travel Berkey.; Berkey Fluoride Filters (PF2) attach to the Berkey Black filters (BF2) and reduce fluoride and arsenic. PF2 filters and are compatible with all Berkey water filter systems.; Each Berkey filter element has a life of 3,000 gallons: Thatâs an incredible 6,000 gallons for a two-filter system and 12,000 gallons for a four filter system!; Each set of two Berkey PF-2â¢ fluoride water filters should be replaced after 1,000 gallons (3,785 liters).