Hello,
We'd be happy to help but we'll need to see the attachments on either side of the metal channel. Your (29 9) stamp is also outdated, so I would recommend weighing the window sash so that we can determine the spring strength needed to support your window. Thank you!
With this combination of attachments, you could have either an S380-30 or S385-30 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.
Unfortunately, you'll need to weigh your sash to determine which option you'll need. There is a chart on the product page that explains how to choose your option based on the sash weight. There is no other reliable way to make sure your balances are calibrated correctly. If you choose the incorrect spring strength option, your windows won't operate properly and could cause damage.
Thank you and let us know if you have any other questions or concerns.
