Help with choosing spiral balance replacement part

A home owner from Ohio says:

I need help in choosing the correct sprial replacement part for a tilt, single hung window. I have detailed pictures and measurements.

Thank you,

Customer images of their plastic spiral balance.
Profile picture of Donna
Donna from SWISCO responded:
Hi Jeffery, thank you for sending such great images.
I do believe you are on the right track with the blue tip Series 600 balances.
Measure the internal spiral rod, I would try to get close to that length if possible.
The S600-27 has a 27" tube length and a 28" internal spiral rod.
The S600-28 has a 28" tube length and a 29" internal spiral rod.
Please let us know if you need any further help.
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