Combo custom ribbed

A home owner from Pennsylvania says:
June 25, 2021
A Swisco rep said this has to be a custom.

I am looking to replace a broken part on a Weathershield 2000SH single hung window.WS called it a jamb liner. Someone else called it a block and tackle sash balance.
It is a spring with line and pulley attached. Holds the window open.

30TG is stamped on the cover. It looks like the Series 751. But the balance screws in at the top, does not slide in like the video. The balance cover appears to be 31"s long. Let me know if these pics help or if you need more info.

I would need two
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Paul from SWISCO responded:
June 28, 2021

Hello there. It's possible you may be able to use our S751-31, but you'll have to compare the metal channel dimensions to ensure they match. Our Series 751 has a ribbed metal channel that is 9/16" wide by 5/8" high. Please review. 
31" Series 751 Channel Balance
31" Series 751 Channel Balance
S751-31
$12.05
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