Spiral balance for tilt window

Hello there. Based on the dimensions I'd say you have an S600-28 Spiral Balance. However since the green tip is more characteristic of the 3/8" diameter Series 900 balances, I'd double-check the diameter of the outer tube to be safe. Older spiral balances with that plastic sheathing can be tricky to measure the diameter on, but do your best. If it is indeed a 5/8" Series 600, you'll need to weigh the window sash the balances support to determine the color tip option you can use. Let me know if you have questions.