Coil balance assembly

We'd like to help, but I am afraid we can't narrow down what you need from this alone. Can you show me the pivot shoe that these coils connect to? The identity of the pivot shoe will tell us the identity of the coil springs you need. We'll do our best to help from there. 

This is a 15-199 Pivot Shoe, which uses either the 1/2" thick Series 160 springs or the 3/8" thick Series 165 springs. Measure the thickness of your old springs, compare and see which Series you need. To know what spring weights to select, look for stamps on the springs, near the tongue. If there is none, or you are uncertain, weigh your window sash. Give me that exact weight and I can work out what you need. 

I'm still not certain how thick your spring is, be it either 3/8" or 1/2". I would also avoid estimating the sash weight, you want to get as precise a weight as you can.

The rule of thumb in general is to divide the sash weight by how many springs support it. For example, if you had the 3/8" thick Series 165 and your sash weighed exactly 8 pounds, you would divide 8 but the number of springs in the window; in your case, you would want the 4 pound option.

That is just an example, though. I would recommend getting an exact weight and confirming the Series before you make your choice.