Window spring

Thanks for posting. This looks like a 15-087 Pivot Shoe, which uses Series 180 Coil Balances. The mounting bracket is the 16-024. The diagram below shows how all these parts install.

Series 180 coil balance diagram

As far as how many coils per side you need, typically extra coils in this system are housed within 15-086 Tandem Blocks that stack atop the 15-087 shoe. I think the best thing to do here is to give me the exact weight of the window sash. Give me that exact weight, and I can tell you the coils you need. 

Great, thanks! So for a 12 pound sash, you only need one 6 pound spring on each side. With that in mind, I'd suggest our S180-6 and 15-087 carrier. The tandem carrier would not be required.