Replacement window part

We sell a variety of coil balances, but I cannot determine what you have based on this photo. Can you show me a picture of the pivot shoe? That will act as a sort of "key" and allow me to determine everything else you need. Thanks!

The pivot shoe is the squared, hard plastic piece that holds the coil spring in its place. It should look something like the one that is in the diagram below. 

detail of 15-192

We can start with our search by seeing the pivot shoe you have currently in your windows and we will take it from there.

Looks like that's just the cover. The pivot shoe should be below that. The spring is housed in the cover you're showing us, and then it extends down and attaches to the pivot shoe. 

Most covers more or less look the same, so we cannot be sure what you have from that. The pivot shoe is the most tell-tale clue, since they're all fairly unique.

Your pivot shoe looks similar to our 15-191. This uses the 1/2" thick Series 160 coil spring. Ultimately, you will need to remove the pivot shoe in order to compare its dimensions to ours, as well as how the coil spring attaches to the pivot shoe. Our Series 160 simply hooks into the 15-191 using that "T" shaped end.

Finally, the spring will have a weight or code stamped on it. You'll need to get your stamp to determine the right Series 160 option, assuming this is the balance you want.