Intended for use outside your ionizer with an external housing (not included). Fluoride in drinking water is unwanted contaminant for many of us. AlkaViva’s proprietary solution is the Fluoride Shield. It is NOT made of activated alumina or bone char and so not pH or temperature sensitive. It employs the latest cutting edge technology. The external fluoride water filter reduces fluoride to very low levels in laboratory testing. Capacity approx. 700 gallons.