Anderson Sash Balance

I have a 28" width by 37" height double hung Anderson replacement window that are 20+ years old with 3" by 6 3/4" sash balance shown. They are marked on the side shown with 11600-17 and on the reverse side with 11600A-3. On the flange the following 549 1 is to the left of the hole and J56 2 90 is to the right. Can you tell me which sash balance to purchase? Thank you