Windows balance 28.5inch

Thanks for posting. These are called spiral balances. You'll need to measure the outer tube diameter to calculate what series you need--if it's 3/8", use the Series 900. If it's 5/8", use the Series 600. See the video below for details. For a balance length that ends in a half-inch increment, round up; so in your case, use a 29" balance as a replacement. Let me know if you have any further questions.