HTH® Pool Care Chlorine Stabilizer 4 lbs.Help protect and extend the life of chlorine in your swimming pool water and ensure healthy swimming. Protects chlorine against sunlight Helps chlorine last longer Compatible with all swimming pools Extends chlorine life Helps slow down the effects of direct sunlight on chlorine in swimming pool water. Easy application Simply add HTH Chlorine Stabilizer directly to your skimmer. Youre all clear with HTH For best results, use HTH 6 Way Test Strips