Would 351 Channel Balance work to replace these?

A home owner from 22042 says:

Hi! We have several windows that need new balances. Would the 351 model work to replace our old ones? The size is 25". These are Nuprime brand windows

If yes, do you have these in stock? Also, all of these windows have only one channel balance on the left side. Was there supposed to be one on each side?

Thank you for your time.

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Lauren from SWISCO responded:

Hello, thank you for posting! 

As long as the depth of your bottom shoe attachment measures 1", then you will need the Series 351 . We also have our Series 390 which is a similar style, but the bottom shoe is 1-1/8" as shown below: 

Comparison of the S351 and S390 balance shoes.
Comparison of the S351 and S390 balance shoes.
You will also need to determine which strength option is needed. Is there any numbers stamped on your balance? If not, you will need to obtain the weight of the window sash. 
The stock of these balances will depend on the size and series. All windows use a total of two balances with one on each side of the window channel. Please let me know if you have any questions. 
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