Balance spring identification help

Home Owner from USA, Florida

May 15, 2025 1:50 pm

I have 20 year old windows. The marking on the balance springs say 28C USB. The width measures 1/2 inch. Can you recommend a replacement?

2 user uploaded images

4 Replies

Jasmine from SWISCO

May 16, 2025 11:13 am

Thanks for posting! There are a few possible recommendations we have for the balance you have here. To narrow them down, I'll need to know the length of the metal channel, excluding the top and bottom attachments. Please also confirm the measurement for the depth of your bottom shoe (the front to back measurement).

Home Owner from USA, Florida

May 18, 2025 4:57 pm

The metal channel is 29 inches long and the depth of the bottom shoe is 3/4"
Thanks so much for your help!

Jasmine from SWISCO

May 19, 2025 11:06 am

Thanks for confirming. Your window balances can be replaced with the S378-29, S380-29, and the S385-29. To determine which of these is the correct replacement, you'll need to double check the depth measurement of the bottom shoe. Take a look at the diagram below for reference.

You can likely use the 2830 stamp option but it would be advised to confirm that the sash weight falls between 16 to 23lbs.

Comparison of the S378, S380 and S385 balance shoes.