30.3 BSI




Hello,
With this combination of attachments, you could have either an S380-31 or S385-31 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom attachment, and the Series 385 has a 1-3/32" attachment. You'll also need 3030 spring strength options for your replacement balances.
Thank you and let us know if you have any other questions or concerns.





In that case, I would recommend weighing the window sash on a common bathroom scale and following the chart under the balance product description to confirm the correct strength option for your window.




Then you'll need a 3040 strength option for your balances to support a sash weight between 23 and 28 lbs.