Unknown window make
This is a Coil Balance system. Specifically, this looks like a 15-087 Pivot Shoe and 15-086 Housing Pivot; these parts use our Series 180 Coil Balances. You'll have to look for stamps on the springs to indicate what spring weights you need. If there are none, or you uncertain, obtain the exact weight of the window sash. Give us the exact weight, and we'll work out what you need.
Again, this looks like the 15-087 and 15-086, which use the Series 180. But without the exact sash weight, I can't confirm what spring weights you need.
No worries. If the sash weighs 19.6 pounds, then I think (4) of our S180-5 5 pound springs should work nicely. Use a pair on either side of the sash, to total 20 pounds of overall support--this is close enough to your sash's reported weight that it should operate smoothly. Let me know if you have further questions. Also see the diagram below that shows how all the components of this balance system come together.
