Window balance 28F USB

A handy person from Fort Myers says:
2 windows with "28F USB" block and tackle. Window weighs 40 lbs. A third narrower window weighs 27 lbs. Need 4 replacements for 40 lb windows, 2 replacements for 27 lb window.
Channel balance
Balance attatchments
Balance attatchments
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Tom from SWISCO responded:
We believe you may need our Series 380 channel balance. Compare the measurements of your balance she to ours to see if this is the correct one you need. We would also like for you to provide us with the precise weight of your window sash.
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