Balance identification

A handy person from Eagle says:
good afternoon, I live in the Boise Idaho area I have a job I'm working ona housethe original windows were made by Certainteed when I took out the balancing springs on the single hung windows the only information I can see on this spring is 31 9 and then a sideways stamp B S I and then another's stamp the letter O, the letter F, but there together. So it readslikethis 31 9 OF could you please give me some guidance on a replacement balancing spring. thanks in advance for your time I could also send pictures if they were needed
User submitted photos of a window balance.
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Tom from SWISCO responded:
We should be able to help with this, though your balance will need to be custom made. Before we continue, can you just tell me how many you need? Once we know that we can send you a custom balance order form.
A quick learner says:
Thanks for the response but I guess I'm completely puzzled these balance Springs look no different than other balance Springs I have seen on the internet why do they need to be custom? I have all different sizes of windows so the balance Springs would be different in most of my windows. I believe that the metal u-shaped frame as well as the spring is fine but I'm having problems with are the roller wheels are split I was hoping to replace the whole balance spring but if it's a custom nightmare can I just buy the replacement rollers?

Profile picture of Tom
Tom from SWISCO responded:
This balance has a unique configuration, that's all. There are many variations that all have subtle differences, however these differences still make an impact on how it functions. Our customer orders are very simple, however. All we do is send you a link to a special part that you can add to your cart. From there, you place your order as normal. All the complicated stuff is on our end.

If you have other balances like this, however, then we will need the same information you posted here. Let me know how you wish to proceed.
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