Key item features 1.4 AUTHENTIC BLACK BERKEY ELEMENTS BB9-2 REPLACEMENT ELEMENTS FOR BERKEY GRAVITY-FED WATER FILTER SYSTEMS- Black Berkey Elements can be used with Big Berkey, Berkey Light, Crown Berkey, Imperial Berkey, Royal Berkey, Go Berkey and Travel Berkey Systems. 2.NDEPENDENT TESTING- Black Berkey Elements (the original BB9-2) are composed of a unique, proprietary blend of multiple media types backed by testing from accredited, third-party labs. Black Berkey Elements remove or dramatically reduce over 250+ typical contaminants that could be present in freshwater sources—no electricity, tools, or plumbing are required. 3.ECONOMICAL, LONG-LASTING- Black Berkey Elements provide filtered water for just pennies per gallon. Each pair of Black Berkey Elements lasts for up to 6,000 gallons before replacement is recommended.