spiral balance

Thanks for writing in. In order to determine what series spiral balance you need, you need to measure the diameter and length of the outer tube. If the diameter is 5/8" and the length is 30", then S600-30 would be correct. If your color tip does not match one of our options, you will need to weigh your window sash and refer to the chart on the product page. Let me know if you have any further questions.