Clorox Pool&Spa XtraBlue 3 inch Chlorinating Tablets are multi-functional swimming pool chlorine tablets that work to kill harmful bacteria and unsightly algae. Each tablet s slow release formula contains stabilizer and protects your pool surfaces from scale and corrosion. Use weekly in skimmers feeders or floaters. Always apply chemicals per label directions. Use the free Clorox Pool app to get personalized product and dosage recommendations for what your pool needs. Simply enter your test results or scan a Multi-Use Smart Strip. Then apply these chlorine tabs as recommended.