help me order the right part

A quick learner from portland, or says:
Hi - I'm looking to replace a few balance springs on vinyl window mfg in 1994. It looks like they are Caldwell markings 31 9 38#, length 32". Guessing S380-32 opt 3165 would work. The shoe is ~ 1" x 1"
User submitted a photo of window balances.
Profile picture of Tom
Tom from SWISCO responded:
I can't tell what Series you have, as you only show the top nylon piece. I also need to see the bottom nylon piece. Can you also confirm the weight of your window sash? Thank you!
A quick learner says:
Here's the other pic, I don't have the sash with me but it's a heavy 3x3 window, I'd say at least 35lbs
User submitted a photo of window balances.
Profile picture of Tom
Tom from SWISCO responded:
Great, thanks. I've narrowed this down to two possible channel balance Series: either our Series 380, like you said above, or our Series 385.

Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 380 uses the 15-005 while the Series 385 uses the 15-004. Personally, it looks more like the 15-001 to me, but you said you think it's the Series 380 so now I'm not as sure. Carefully compare the dimensions we show below to your own shoe and see what you think.
Comparison of 15-004 and 15-005
Comparison of 15-004 and 15-005
How to Replace a Channel Balance Attachment
How to Replace a Channel Balance Attachment
VIDEO
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Classifying Channel Balance Fittings
Classifying Channel Balance Fittings
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