Coil balance

Thanks for posting. Looks like you have either a 15-111 Pivot Shoe or its heavy duty variant, the 15-191. This is compatible with our Series 160 Coil Springs. Look for stamps on your coil springs that indicate what stamp weight you need. If your coil springs lack stamps, weigh each window sash that has coil springs you need to replace, and tell us how many coil springs go with each window sash. Thanks. 

Hm, most likely the 160-9 is the right choice. I hesitate only because it's a little unusual for the stamp on a S160-9 to show only a '9' rather than a '9.5'. Essentially the goal with these coil springs is to have half the weight of the window sash being supported on either side. So for instance, if your window sash weighed 19 lbs, you would want (2) of the 160-9. You would install one on each side of the window sash, so that 9.5 lbs of support were on either side of the window, totaling to the sash's overall weight of 19 lbs. If you are ever uncertain in your choices, the best thing to do is to obtain the weight of the window sash.