Weight range for channel balance

A home owner from Carlsbad, CA says:
I used your selection app to find the replacement channel balances for my single hung non-tilt window. I came up with the 23" Series 385 Channel Balance, Product Code: S385-23. The weight number printed on my old channel balances is 2290, but my aluminum sash weighs only 10 lbs. Your recommended weight # is 2220. What replacement weight # should I order?

(One of the old balances has a groove worn in the nylon pulley, making it hard to raise and lower the window. I've attached a pic of the old balances.)
User submitted a photo of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
If the sash is only 10 pounds, then the 2220 option is definitely the way to go. Some stamps, like the one you have, are outdated or use a different rating system. Because of this, it's always safer to go with the weight of the sash itself. Manufacturing codes change over the years, but hard facts never lie.
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