HTH, 35 LB, 3" Stabilized Chlorine Tablets, Sanitizes Pool Water, Stabilized, Sun Protected For Extended Chlorine Life, For Use In Skimmer Or Floater, Protects Against Bacteria & Algae Growth, Active Ingredients: Trichlors-S-Triazinetrione 92.4%, Zinc Sulfate Monohydrate 3.5%, Other Ingredients 7.6%, Available Chlorine 84%.