Spiral balancer measurement

A quick learner says:
November 4, 2015
Hi,
I want to replace the spiral balances in the top sash of my window. I know i need the Series 500 spiral balances in red but do not know what length to order. The sash measures 26.5 inches, top to bottom. I already discarded the old balances so cannot measure them.
Thanks for your help.
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Tom from SWISCO responded:
November 4, 2015
Hello! Can you tell me the size of the visible glass? That will allow us to calculate the proper length.
A quick learner says:
November 4, 2015
it's a six over six. visible glass size is 10" wide by 11.25" high
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Paul from SWISCO responded:
November 5, 2015
For a wood top sash with a 23" high glass in total, I would recommend our S500-24 with a Red Tip.
A quick learner says:
November 6, 2015
Thank you. So, just to confirm, and in case I need to replace any additional top or bottom sash balances in other household windows that vary in size (most old balances were taken out long ago and are not available to be measured)-- the formula for determining the length of the new balance is to add the height of the visible glass panes in the vertical row of the sash?

Thanks again for your help!
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Paul from SWISCO responded:
November 6, 2015
The formula we use to calculate the length of wood sash balances is the glass height plus 1" for the top sash, and the glass height plus 3" for the bottom sash.
24" Series 500 Spiral Balance
24" Series 500 Spiral Balance
S500-24
$9.02
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