Spring balance for 1964 aluminum window

Question

I have non-tilting, single sash aluminum windows that need new balances. The spring attaches under the sash in a plastic bracket. The tube is measuring 9/16 inch, so should I size up to the 5/8 tube or 500 series? And can you confirm they will hook into the bracket under the sash? And do you sell those plastic brackets? I have other windows where they are broken.
Thank you! Photo above is from the bottom of the sash.

Jasmine · Accepted Answer

Thanks for writing in! The 9/16" diameter is considered 5/8" in the trade, so the Series 500 Spiral Balance should be the correct replacement, providing your are confident the measurement is correct.

Since these balances have the same t-shaped cross-piece on the tip of the balance, I am confident our balances will fit into the bracket connected to your sash. If you are looking to replace the bracket, in addition to the spiral balances, I'll need to see it removed from the sash to identify the right replacement. Unfortunately, I am unable to tell from the photos the exact type of bracket you have in your window.

Please let me know if there is anything else I can assist with!