This is the famous Aquafinesse Spa Clean tablet. It's basically a concentrated version of Aquafinesse's famous pool and spa salt solution. This tablet powers through bacteria and biofilm, ensuring that you start over with a pristine and microbe-free spa. This is the product we recommend to most people who come into the store with translucent flakes coming from their jets, but it's also great if you just want to make a clean slate when you drain and refill the water in your spa.