Alenco window balance

A handy person from Austin, TX says:
Looking for a replacement part or the entire window balance for an Alenco white aluminum sash (bottom part moves up and down, no tilting feature) window.

I'll attach some pictures of the plastic end pieces and provide some measurements. The metal channel is 28" long. The stamp on the channel says 2790 JK 31.

Is it possible to buy just the bracket/pulley assembly that attaches near the bottom of the U-channel? If not then I need a quote on the whole balance. Are these best replaced in pairs?? Thank you.
User submitted photos of a window balance.
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Tom from SWISCO responded:
Good morning, and thanks for posting. Unfortunately, the pulley cannot be replaced alone. You will have to replace the whole balance. Before I can recommend which replacement balance you need, I first need to figure out what that bottom shoe is. Check out our 15-001 and 15-002 and tell me which is a closer match.
Comparison of <a href='Channel-Balance-Shoe/pd/Replacement-Sash-Support-Channel-Balance-Shoes/15-001'>15-001</a> & 15-002
Also, we don't have a stamp option that corresponds to 2790. Could you give me the weight of your sash? That will help us determine the best alternative.
A quick learner from Austin, TX says:
Sorry for the delay responding. The sash weight is 28 pounds. 15-001 appears to be the closest match for the bottom shoe. Thanks.
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Tom from SWISCO responded:
Perfect, thank you. Check out the S395-28 with the 2750 option. I've chosen the 2750 option for you. Two balances with this option can carry a window sash weight of 26 through 30 pounds.
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