Channel Balance assemblies

A handy person from Coppell, Texas says:
I need 2 each Channel Balance Assemblies. Markings on old assemblies appears to be 27C, however when measuring the metal portion of the Channel itself, end-to-end, it measures 28". I went to Southwest Glazing Supply Company in Dallas, TX and they said there part number for this was 2740 or 27D but when they did a cross reference with your website they said it was a SWISCO S350-28. I have pictures if necessary. I need to order these parts ASAP. Thanks.
User submitted photos of a window balance.
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Tom from SWISCO responded:
This could be our S350-28, yes. The stamp is not a part number, it's only indicative of spring strength. There is no number on your balance that will tell you what it is, the only thing that will confirm is the style and size of the nylon shoes. From what I see in your pictures, as long as the bottom shoe is the same size as the 15-002, then the S350-28 should be okay.

I would also recommend the 2730 option. You can always weigh your sash to confirm that this is correct.
A quick learner from Coppell, Texas says:
from the info i sent can you tell if this is a S351-28 or a S350-28
Profile picture of Tom
Tom from SWISCO responded:
No, there isn't enough info in the photo to make a positive identification. Here's how you can tell: measure your bottom shoe as shown below. If it matches the 15-002 on the right, you've got a Series 350.
Comparison of 15-001 & 15-002
Comparison of 15-001 & 15-002
How to Replace a Channel Balance Attachment
How to Replace a Channel Balance Attachment
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Classifying Channel Balance Fittings
Classifying Channel Balance Fittings
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