Series 159 Coil Balance Quote

Hello there. If you are certain you need the Series 159 Coil Balance springs, and the sash weighs 12 pounds exactly, then you could use two of the S159-05 5.5 pound springs, one for each side of the sash. This would give you 11 pounds of support overall--being within 1 pound of the exact sash weight works just fine. If the sash weighed a little over 12 pounds though, you'd want to go with the S159-06 6.5 pound springs, which would double to 13 pounds of support. 

If you're not certain the Series 159 is what you need, of course, please send us photos of your old hardware removed from the window, and we'd be happy to determine what you need.