Product Description "Product Description Authentic Black Berkey Elements (also known as BB9-2) address over 200+ typical contaminants that could be present in tap water and raw, freshwater sources like rivers and ponds. A pair of Black Berkey Elements lasts for up to 6,000 gallons before replacement is recommended. Elements may require replacement sooner based upon the quality of influent water. Each additional pair of Black Berkey Elements (sold separately) adds an additional 6,000 gallons of contaminant reduction to your system. If desired, Berkey PF-2 Fluoride and Arsenic Reduction Elements (sold separately) may be installed on each Black Berkey Element. Black Berkey Elements are backed by independent, third-party testing. Elements not for use with saltwater sources or softened water. From the Manufacturer Made for the extreme and enjoyed every day, Berkey systems are the gold standard in gravity-fed water systems. Berkey systems have been the trusted choice of adventurers, relief agencies, preppers, off-grid homesteaders, and families for over 20 years. Berkey gravity-fed water systems are available in 7 sizes and are ideal for use at home, camping, fishing, RVing, or during unexpected emergencies and disaster scenarios. Enjoy delicious, refreshing water for just pennies per gallon." From the Manufacturer Berkey Systems are the World's Most Powerful and Cost Effective Personal Water purification Systems Providing Reliable and User-friendly Water Purification in Both Normal and Hostile Filtration Environments. Moreover, Berkey systems are capable of purifying both treated water and untreated raw water from such sources as remote lakes, streams, stagnant ponds and water supplies in foreign countries, where regulations may be substandard at best. So powerful, this system is able to remove red food coloring from water without removing the beneficial minerals your body needs. Perfect for everyday use and a must in hostile environments where electricity, water pressure or treated water may not be available.