Sustain® W8000040 25 lb Pail 3" Chlorinating Tablets (blue), when used according to label directions, will keep your swimming pool looking great by providing routine sanitizing power all week long. These tablets contain a proprietary erosion modifier that allows them to deliver chlorine more consistently than conventional white tablets (Trichlor). And, Sustain® Tablets don’t contain cyanuric acid (CYA) which can inhibit chlorine effectiveness.