FROG Serene Mineral Cartridges (formerly Spa FROG) are for use in the
FROG Serene Floating Systems, in which pre-filled mineral and bromine
cartridges combine in a floating dispenser to give any spa or hot tub
crystal clear water with a silky feel. FROG Serene Mineral Cartridges
snap easily into a reusable floating holder and when used in combination
with the FROG bromine cartridge, reduces the need for bromine by up to
50%. FROG Serene Mineral Cartridges last an average of four months.
*This is for two mineral cartridges, Bromine cartridges are sold separately.