Peach tree window balance replace

A quick learner from Bloomington, Illinois says:
I need to replace 6 or 8 of these balances. Need to know what is the part numbe to order. Also,any help on how to install would be great. I have tried to work on these and very difficult to get these back in place.

A customer submitted photo of channel balance attachments.
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Paul from SWISCO responded:
Thanks for posting! It looks like you might have our Series 745 channel balance. Is there anything there that matches your balance? If you aren't sure, please give me the length of your metal channel and we can work from there.
A quick learner from Bloomington , Illinois says:
I sent the length already. it is 26.25 inches. But I don't have a number stamped on back so I don't know if it is 25.25-3 or 4 or 5. How would I know? Also ask if someone can help me understand how to install. I worked on these before and very difficult to get the plastic insert screwed into window frame..

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Donna from SWISCO responded:
Very good, that makes sense. The 26-1/4" Series 745 with stamp 25-25.4 is the needed replacement. The 3660 on your original balance is most likely referring to the PeachTree window opening and for a 3660, the 25.25-4 option is the suggested replacement.

I'll ask around the shop for tips on replacing these balances and report back.
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Paul from SWISCO responded:
Unfortunately, we have no instructions as to how to install these balances. I would recommend that you seek the aid of a local professional.
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