2.1 oz. will increase the chlorine level 1 ppm in 10,000 gallons of water. When adding dichlor to pool or spa water for each 1 lb. added, there will be 4 ppm of cyanuric acid introduced in 10,000 gallons. Recommended for outdoor commercial pools and spas. Click on the "Product Details" tab above, to select container size. Available sizes: 25 or 50 lb. pails