Leisure Time Renew Chlorine free Shock is a chlorine free shock of potassium peroxymonosulfate. It can be used in different ways to keep your pool water clean, clear and sanitary. It may work as one of two steps in the "Reserve/Renew System." Part one of the system is Reserve, which is sodium bromide. Then, Renew is applied to activate the Reserve. When the two chemicals interact, they create an active bromine to sanitize. Some spa owners have an aversion to chlorine that hurts eyes and skin. Owners like these can easily replace a chlorine treatment with the "Reserve/Renew System" by Leisure Time for clean, sanitary water without the harsh chlorine chemical. Renew Spa Shock may also be used in conjunction with chlorine chemicals for a strong chemical treatment that extends the life of chlorine. Renew may also be used for spa start-ups or maintenance. Enjoy the chlorine-free use of this strong and versatile sanitizing formula.