Coil balance spring

Question

Hi, I am looking for the coil balance spring in the coil assembly picture for my double hung window. Don't need the plastic parts just the coil balance spring.
The width of the coil is 12 mm (0.472441 inches). I am not sure what weight I need. I am hoping you could let me know which one so I can order the part.
If it helps here is the weight of the both sashes:

Lower sash is 12.56 LBS
Upper sash is 11.90 LBS Thank you
Fred

Paul · Accepted Answer

The coil springs that go with your pivot shoe are Series 152. Look for a weight number on the spring near the end where it's screwed to the pivot shoe. We believe the spring weight number for both the top and bottom sash is 6, meaning you need S152-6.