The H2 Series UltraWater Replacement Filter-Set is for the Athena H2, Vesta H2 and Melody H2 water ionizers. The UltraWater filter is rated for 1,000 gallons, and the Fluoride Shield filter is rated for 500 gallons. This "Annual Replacement 3-Pack" has 1 UltraWater plus 2 Fluoride filters, so you are fully covered for 99.99% of all contaminants, including fluoride removal for about a year.
Change UltraWater filters at least once yearly and Fluoride Shield filters twice a year.
Note: The AlkaViva water experts state that the Fluoride Shield filter is not for sediment and a separate sediment filter may be required to prevent clogging of the very fine Ultrawater filters. If you have a water sediment problem you are probably better off getting the external Fluoride Shield and then inside the ionizer use the standard UltraWater filter set (which has a sediment filter as part of the set).
Read more information about UltraWater filters.