Maintain your hot tub with ease using SPA FROG BROMINE CARTRIDGE YELLOW. These replacement cartridges were designed for the FROG Serene Floating System and provide enhanced sanitation when used with FROG Sanitizing Minerals. Lasting 2 to 4 weeks each, they reduce bromine use by up to 50%*. Keep your hot tub water clean and clear with FROG Serene Bromine Replacement Cartridges.