CCH® 23227 25 lb Cal-Hypo 3" Endurance Chlorinating Tablet 68% Pail. CCH® Endurance Tablets are non-stabilized, and do not contain cyanuric acid. Stabilized sanitizers like trichlor contain cyanuric acid. Cyanuric acid can help stabilize pH and will be measured in a pool water total alkalinity test, but carbonate alkalinity is needed to protect pool surfaces. Low carbonate alkalinity can lead to corrosion and plaster damage. The calcium in CCH® Endurance Tablets helps to protect the plaster, extending the life of the pool.