Channel Balance options

A quick learner from Olalla, WA says:
February 20, 2013
Hello. I'm needing to replace 8 pairs of channel balancers. They seem to be series 351 type, with a 22 in. long channel.

The number stamped on them is 21 S (with "B.S.I." stamped vertically. )

I'm wondering what strength or weight range I should use. The sliding window pane measures 44 in. x 25 in., in double paned with aluminum frame, circa 1984.

Thank you,
Gary
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Casey from SWISCO responded:
February 20, 2013
Thanks for posting! I don't recognize a stamp of 21 S. Could that S be a 5, perhaps? Either way, you may want to weigh your window sash to be sure and compare it to the rating options shown for the S351-22.
A quick learner from Olalla, WA says:
February 20, 2013
No, it's definitely an 'S'...
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Casey from SWISCO responded:
February 21, 2013
Okay, then we will need to figure it out by weight. Please remove the window sash and place it on a scale, we will need the weight of the window sash in pounds in order to determine the proper stamp option for you, as this denotes the strength of the replacement balances.
22" Series 351 Channel Balance
22" Series 351 Channel Balance
S351-22
$9.91
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