What is this tilt window balance?

A home owner from Oviedo, fl 32766 says:

Need a replacement balance. Maybe model 770. Overall length is 22" but stamped as 21F, see pictures. Can you advise of correct replacement part?


User submitted photos of a window balance.
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Paul from SWISCO responded:
Thanks for posting! I agree, I think our Series 770 looks like a good match. I'm not so sure about the stamp though. What is the weight of your window sash? I'm thinking you might need a 22F option, but since that is not standard, such a balance will have to be custom made. I think it's best that we know what your window sash weight is before we go any further down that road.
A home owner says:
The weight of my window sash is 29.4 lbs. Can I use a standard size, 22 inch long, and replace the spring with the one from the old balance?
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Tom from SWISCO responded:
Ah, I see. I do not recommend trying to switch springs. There is a lot of tension on these springs and they are not meant to be replaced like that.

I was right -- you will need a 22F option. Take a look at this Custom Channel Balance Request Form that I have started for you based on your specifications and fill out the rest of the information. One of our representatives will get back to you with a price quote shortly thereafter, and you can decide what you want to do from there.
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