This CRL Tubular Spiral Window Balance for tilt type windows will replace a 9/16 inch (14.3 millimeter) metal or plastic tube balance with a sash load capacity of up to 35 pounds (15.8 kilograms). The 9/16 inch (14.3 millimeter) size of the metal tube is commonly referred to as 5/8 inch (15.9 millimeter) in the industry. While this balance is packaged and sold individually, it is our recommendation that both balances in the window be replaced at the same time.How to Order Tubular Spiral Window Balances1. Check the tube diameter of the metal or plastic tube on the old balance.2. Measure the tube length from the end of the balance to the bottom of the colored nylon bushing only. Do not include the rod extension.3. Check the color of the nylon bushing.4. Verify that the rod extension protruding from the nylon bushing matches what is shown.5. Match tube diameter, tube length, nylon bushing color against the information shown next to the Catalog Number. If all agree, and the rod extension matches the one in the photo, then this is the correct balance.