The @ease Inline Smartchlor System is made for the Caldera Vacanza Series and Marquis spas. It is a sanitizing system that keeps your spa water clean, and fresher than ever. These self-dispensing cartridges take care of the water for you, so that your water maintenance becomes less of a hassle. The silver cartridge contains the smartchlor and should be replaced every 2.5-4 weeks-depending on the size of the spa and how much it is used. The blue cartridge contains minerals that work together with the smartchlor to ensure maximum sanitization, it should be replaced every 3-4 months (during drain, clean, refill).

These are singular @ease Inline Smartchlor Cartridges.