Berkey PF-2 Fluoride/Arsenic Filter, 2-Pack Fits Black Berkey purifiers only Removes: Fluoride, Arsenic V and pre-oxidized Arsenic III, as well as other residual heavy metal ions Simply screw the PF-2 Flouride filter into the Black Berkey filters It is recommended that each set of two (2) elements be replaced after 1,000 gallons