Please assist

Hello there. This looks a spiral balance for a tilt window. These balances are first distinguished by the diameter of the outer tube. If it's 3/8", you have a Series 900. If it is 5/8" (or 9/16") you have a Series 600. At first glance, your spiral balance's outer tube looks closer to 5/8", but pictures of measuring tape can be deceiving, so please double- and triple-check to ensure this is right. If so, it would be a Series 600 balance. If the outer tube, up to and not including the colored tip, is 29", then this is an S600-29. For a color tip option, choose red. Let me know if you have any questions.