replacement window balance

A handy person from FL says:
August 27, 2017
Hello, the window balance is 12.5" long X 1/2" X 5/8"
It has stamped 12-1 W as you see in the attached photo.
Please let me know which part number should I order.
After searching your website I think that the S377-13 is the correct one.
Please advise!

Thank you,
-John
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
August 31, 2017
I agree, our Series 377 looks like our best match. However, if the length of the metal channel is 12-1/2" long, it will need to be custom made.

We can do this for you but before we begin, can you just tell me how many you need?
13" Series 377 Channel Balance
13" Series 377 Channel Balance
S377-13
$9.34
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