This is a double hung window and I think it is a Sears brand

Hello!

Thank you for reaching out to us. This pivot shoe isn't something we sell but we do have an alternative which would be the 15-259. This part is designed to use the S159 coil springs and we also have a video that will walk you through the replacement process which I highly recommend watching. Take a look and let us know if you have any questions. 

It sounds like you have a double coil set up. If that's the case, the two springs are usually screwed to the side of the pivot shoe. 

The top sash follows the same principle, yes. You just want to make sure it also uses the same style of shoe as the bottom sash. 

I'm afraid your old coil springs aren't compatible with the 15-259 pivot shoe. You'll need the Series 159 specifically. 

You can certainly use one spring per side of the window. To determine the proper weights, you will want to divide the sash weight by two. Let me know if you have any other questions! 

With a sash weight of 21.1 pounds, you can use one S159-10 10.5-pound spring on each side of the window. This will total 21 pounds of overall support. Since you'll be using one spring per side, see the 15-255 single coil support. 

I'll be here to help if you have any other questions!