Spiral window balance

Your balance looks close to both our Series 600 and Series 900. However, I do have a question. Was this balance encased in some sort of plastic tube? I ask because spiral balances usually are not made with an exposed spring. If it does come encased with a balance tube, we will need to know the tube diameter of it so that we can recommend the proper balance. 

Thanks for the reply. So if the outer tube is 27-1/2" long, it's best to round up to 28". So you'd need either the S900-28 or S600-28. It's a bit tricky to measure the diameter of the tube with these old plastic tubes, but do the best you can. The S900-28 has a diameter of 3/8", while the S600-28 has a diameter of 5/8". To know what color tip option to select, weigh your window sash. You can then match that exact weight with one of the weight ranges listed alongside each color tip option on the product page.

No, that concept only works for coil springs. If your sash weighs 20 pounds, then you would need to purchase a spiral balance for each side of the window that can accommodate a 20 pound sash weight. 

I hope this clarifies any confusion that may have come up. Let us know if you have any further questions.