single hung window balance spring replacement

Question

Please identify the appropriate window balance spring needed.
Length: 24"
Stamped Code: 23 5 BSI pc
Pics of attached

Jasmine · Accepted Answer

Thanks for writing in! Your balances appear to be either the S351-24 with a 1" shoe or the S390-24 with a 1-1/8" shoe. To determine which series is needed for your window, look over the dimensions from the diagram below to confirm the depth of your bottom shoe.

You'll need to select the 2350 stamp for a window weighing 23 to 27lbs.

Comparison of the S351 and S390 balance shoes.

You'll need to select the 2350 stamp for a window weighing 23 to 27lbs.

Comparison of the S351 and S390 balance shoes.