99% Trichloro-s-triazinetrione - Available Chlorine: 90% Compressed 3-inch (8 oz.) slow dissolving chlorine tablets with sanitizing power of 90% available chlorine and built-in chlorine stabilizer to maintain proper chlorine levels in sunlight. For use in automatic chlorinators, floaters, and skimmers. Kills Bacteria, Destroys Organic Contaminants and Controls Algae Sun Protected for Extended Chlorine Life Concentrated Stabilized