Need a new one of these channel balance

A quick learner from New Smyrna Beach Florida says:
I need one with a stronger spring I think. My window doesn't stay up with one I grabbed from another window that has same part number and window measurements.
Thumbnail of the uploaded file named Wingless Balance Shoe
Thumbnail of the uploaded file named Channel Balance Assembly
Thumbnail of the uploaded file named 21 12 BSI Stamp
Thumbnail of the uploaded file named Channel Balance Shoe
Thumbnail of the uploaded file named Wingless Top Guide
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Jasmine from SWISCO responded:

Thanks for posting! Your channel balance assembly resembles either the S351-22 with a 1" shoe or the S390-22 with a 1-1/8" shoe. To determine which series is needed for your window, look over the dimensions from the diagram below to confirm the depth of your bottom shoe.

Comparison of the S351 and S390 balance shoes.
Comparison of the S351 and S390 balance shoes.

I'm sorry to say that I would not be able to determine if the stamp from your balances is incorrect for your window. The stamp on the balance is how we determine the weight range the balances should be able to carry to support the weight of your sash. However, we are unable to cross-reference your stamp, unfortunately.

That said, you'll need to obtain the exact weight of your sash to determine the exact stamp option you need. 

There is a chart that lists the weight ranges each stamp option can hold.

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