[High-efficiency Filtration]- This water filter elements set is a replacement for Gravity Filtration System filter, have passed a high-standard examination by authoritative institutions, Efficiently reduces chlorine, fluoride, heavy metals, taste and odor, sediments, large particles and other harmful substances. Clean and healthy water can be enjoyed outdoors at any time. [for BB9-2 Black Filter]- for BB9-2 Black Filter is made from high-grade High-quality materials, Compared with ordinary granular activated carbon, it has higher adsorption capacity, efficiently reduces fluoride and chlorine, filter impurities. [for PF-2 Fluoride Filter]- for PF-2 Fluoride and Arsenic Reduction Elements replacement filters adsorb fluoride, arsenic(V) and pre-oxidized arsenic(III), and other residual typical heavy metal ions. [Perfect Compatible]- This set of filter elements compatible with Berkey Gravity Filtration System filters, Compatible with FOR Doulton Super Sterasyl and Traveler, Nomad, Royal, King, Big, Imperial and Crown Series. We recommend you replace for PF-2 water filter every 1000 gallons and for BB9-2 black filter every 6000 gallons, to achieve performance, or you can replace it based on your water condition. Material: plastic colour: white+black Package Contents: 4 x for BB9-2 Water Filter 4 x for PF-2 Water Filter