This is the part I would like to replace. I believe the replacement part is 15-177.

I can't determine what pivot shoe you have based on this photo, unfortunately. The original is too obscured and broken to see. We'll need to see this out of the window to properly ID, or at least to see one in undamaged condition. Can you provide that for me?

That's a huge help, thank you! I do recognize this assembly. Looks like you have the old Simonton brand coil balance. They no longer make this, but we have two possible solutions for you to consider.

The first is our 15-192 pivot shoe, along with our Series 170 coil spring (and other parts related to its store page). This is a Certainteed brand part but I have had customers in the past tell me that they got it to work after grinding down the front of the face, which sticks out just a little too far for this window. You may also need to reuse the center metal cam, since the new one may not fit with your existing pivot bar.

The other option is a more modern replacement that I think works just as well, if not better, since it's not prone to breaking in half like your old one is. The video below will go into more detail. This will explain exactly what parts you need to buy and how you can install them in your window. Just note that you will need the exact weight of your sash on hand in order to calculate the proper spring strength. You want to divide that weight by how many springs support the sash, then pick accordingly.

You're welcome! Please do let us know if you had any follow up questions. We're always here to help.

Sure, so if you're going with the Series 159 then I recommend using the 6.5 weight option S159-06). Each spring holds 6.5 pounds each, so one on each side gives you a total coverage of 13 pounds. That should be perfectly sufficient for your sash weight.