What spring balances do I have? 2790/2740

A contractor from houston tx says:
i am a gen contractor with limited spring balance experience. i have watched the videos and have learned a lot. i need three balances to replace broken ones.

two of them say "2790 FK 31"

one says "2740 bs LH"

all three are have broken internal or other parts, i prefer to replace whole balance asssembly, and if reccommended will replace both side balances to have equal pressure on window. thanks for your time.
User submitted photos of window balances
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Tom from SWISCO responded:
Thanks for posting! Alright, looks like we have a few things to consider with these balances.

The first thing I'd like to address is the nylon attachments. Are they all the same across the three balances? It looks like your top attachments are winged, while your bottom attachments are not. Before we can start on that, though, I just need to confirm what the bottom shoes are.

Please look at the measurements for our 15-001 and 15-002 bottom shoes and note their depths. As you can see, they are 1-1/8" deep and 1" deep, respectively. Which measurement more closely resembles your own shoe?
Comparison of 15-001 & 15-002
I would also like you to confirm the lengths of the metal channels as well as the weight for the window sashes that correspond to each balance. That will help us determine what option you need. Thank you!
A contractor from Houston says:
1 1/8th depth on all foot pieces. All metal channels 1/2" by 28". I don't have weight of sashes just the broken spring balances. I can give you rivet placement from old springs ,does that help?
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Tom from SWISCO responded:
Great, thanks for the information. Unfortunately, we're going to need the sash weights in order to get you the right options. You can determine this by removing the sashes from the frame and placing them on a scale -- any common bathroom scale should do.
A contractor from houston says:
hello again,

sash weights as follows

2740--- 23.8 lbs

2790--- 24.8 lbs

would like to get two new for each window


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Tom from SWISCO responded:
Thanks for getting back to us. For both of those balances, I would recommend our 2740 option. Two balances with this stamp can carry a window sash weight of 19 through 26 pounds. The balance you need to order is the S395-28 with the option 2740. Let me know if you have any questions.
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