This fast-dissolving granular formula sanitizes and disinfects spa water and is part of the EZ SPA once-a-week water care program. Available in a convenient 1 lb. size and in the EZ SPA CARE KIT. Add EZ BOOST at a dose of 1/2 oz per 100 gallons. E-Z boost has been re-labeled and is now E-Z RES. The same great product just a new design!