Poolife NST Prime Chlorine Tablets (20.2 lb) - 3-Inch Slow Dissolving Pool Sanitizer for Swimming Pools & Spas - Effective Water Treatment for Crystal Clear Water All Season

The CYA in our pool was way too high so we could not use stabilized chlorine. I ordered these undtabilized tablets and they have worked fantastically. The CYA has come down because we've had a lot of rain and I've been able to keep the chlorine up with these large tablets. They are very easy to use, I just put them in the skimmer basket.