390 series weight

A handy person from California says:
I have a balance that looks like the 390 series. Both ends look the same and mine has stampted 2790 which is a 28 inch but it does not show on the available size. What is unique about the 2790?
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Paul Sr. from SWISCO responded:
See if there are two more numbers following, those will give you the exact weight of the spring. If you're not sure, send us pictures and we'll see how we can help.
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Donna from SWISCO responded:
Or, remove the window sash and place it on a scale to get the weight in pounds. I can determine the proper strength balance from the sash weight.
A handy person says:
2790 gk 30 is what is stamped
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Donna from SWISCO responded:
We will order 2760 stamp option in for you, this will hold a sash weight of 30 through 33 pounds.
This information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.
I will post again as soon as they are ready for purchase, approx 3 week lead time
A quick learner says:
ok i need the two balances and 4 Product Code: 18-008 top sash guides.
A quick learner says:
So do i order these or do you order them and then let me know when there in?
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Donna from SWISCO responded:
I will post again as soon as the 2760 stamp option are ready for purchase
A quick learner says:
I will weigh the window just for good measure.
A home owner says:
They weight 30.4 pounds.
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Dave Sr. from SWISCO responded:
The 2760 balance will hold the weight of your sash.
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Donna from SWISCO responded:
The 2760 stamp option for the Series 390 is now available online:

A quick learner says:
Thank You i just placed the order.
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