Need CMC 26-3 non-tilt window balance

Thanks for posting. I'm confident we can help, but I need to verify further details. Can you remove the balance from the window and show us a few detailed photos of its underside, or 'guts'? I need to clarify one feature before proceeding. Many thanks. 

This is a huge help, thanks again! Based on what I see here, you have either our S380-27 or S385-27, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

Comparison of the S378, S380 and S385 balance shoes.