window ballast replacement

A home owner from USA says:
attached are some pics that might help
if you can match what i have I'd like a set
some markings are :

21 3
3S1 maybe ?

User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Hello, Norman. We can replace this balance, but it will have to be a custom order. Before we begin, can you just tell me how many you need?
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