Window Balance

Question

Trying to identify the right window balance. I know it is a 1/2" Channel Balance, 31 inches long, and it looks very similar to the S351 and S390 (same shoe piece and other end piece and spring and string configuration).

The markings imprinted on the existing balance include 3040 BJ and 3.S.I.

Any idea on what I need

Jasmine · Accepted Answer

Hey there,

Thanks for posting! Without photos of the balances, I cannot confirm with certainty that these are the series balances you might have. If they have a non-winged top and bottom attachment, then you likely have one of them.

To determine if the S351-31 or the S390-31 is the correct one for your window, you'll need to confirm the measurement for the depth of your bottom shoe. Take a look at the diagram below for reference.

Comparison of the S351 and S390 balance shoes.