Channel balance 2410A

A home owner from Saint Paul, MN, USA says:
I am looking to replace the hardware pieces shown in the photo.
Not sure when I am measuring if I should only measure the metal part or include the plastic pieces on the end in the measurements?
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Emily from SWISCO responded:

Thanks for reaching out to us. It looks like you have either the Series 351 or Series 390 depending on the depth of the bottom shoe. You'll have to measure as shown below to determine the proper Series. If the balance is stamped with the number 2410, the metal channel should measure 25" long. 

Let me know if you have any questions!

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

A home owner from Saint Paul, MN, USA says:
The depth of the bottom shoe of the pieces I need to replace doesn't look like either of those pictures.

The metal channel is definitely 24 1/2 inches long. The number stamped on it is 2410A

Any further insight on where I should look for replacements?
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Thumbnail of the uploaded file named top fitting
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Emily from SWISCO responded:

Can you tell me what you got for the depth of the bottom shoe? It could be that it was worn down over time from use depending on the dimension. 

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