About this item .BLACK BERKEY ELEMENTS FILTER TYPICAL CONTAMINANTS THAT COULD BE PRESENT IN TAP WATER AND RAW, FRESHWATER SOURCES SUCH AS LAKES, RIVERS AND PONDS- Choose only Black Berkey Elements. There are no substitutes for Berkey performance and quality. .FLUORIDE AND ARSENIC REDUCTION- Berkey PF-2 Fluoride and Arsenic Reduction Elements are designed for use in conjunction with Black Berkey Elements to adsorb fluoride, arsenic(V) and pre-oxidized arsenic(III), and other residual typical heavy metal ions. .ECONOMICAL, LONG-LASTING- A pair of Black Berkey Elements lasts for up to 6,000 gallons before replacement is recommended, depending on the quality of influent water. Each additional pair of elements (sold separately) adds an additional 6,000 gallons of contaminant reduction to your system before replacement is recommended. Berkey PF-2 Fluoride and Arsenic Reduction Elements should be replaced after 1,000 gallons of use, under normal conditions.