I found "36C, B51" manufacturer of the window; M&W(or Ply Gem)

Thanks for writing in! I'm fairly confident your window balances can be replaced with the S795-36 with a 36C stamp. 

These come with a 1-1/4" closed cam shoe attached to the bottom of them; it measures 1/2" deep. To confirm this is the correct fit, carefully look over the specifications. You'll also want to be sure to take a look at the cam to see if it is closed or opened on the back.

If the cam is opened, you'll also need to purchase the 15-195B. These are sold separately from the balances but they are fairly easy to swap out.

Please let me know if your shoe does not match the dimensions for ours.

Dimensions for 15-195B

Alternate view of 15-195

Alternate view of 15-195B