Specs for window balance

A home owner from Dublin, Ohio says:
The balance is 17" long (not including the nylon ends). Has a marking/stamp of "1620 and what looks like the top half of a percent symbol.

Thank you
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Emily from SWISCO responded:

Hello!

It appears you have either our S351-17 or S390-17 channel balance, depending on the depth of the bottom shoe. The Series 351 comes attached with a 1" deep shoe and the Series 390 comes attached with a 1-1/8" shoe. Measure as shown in the image below to determine the best match. You'll also need the 1620 strength option, based on your 1620 stamp.

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