Need replacement for 21-inch Window Channel Balance, marked "21 B"

A home owner from Roseville, California says:
June 27, 2018
Hello, I need to replace 12 of these 21-inch WIndow Channel Balances. Please advise on the correct part # for replacement.

Thank you,
Ren
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Tom from SWISCO responded:
June 29, 2018

Hi, Ren. Based on the length and other info you provided, you would need S350-21 with a stamp of "2020." It's odd for the new stamp, 2020, to be so different than the old stamp, 21B, though. Can you verify that the metal channel measures 21" by itself? You may also want to check the weight of your window sash and send it to me.
21" Series 350 Channel Balance
21" Series 350 Channel Balance
S350-21
$9.59
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