Replacing window balance

The thread in the window balance on one side of a window broke. The window is about 25 years old so I assume I should probably replace both window balances. However, I cannot tell from your website pictures which balances to order. The metal portion of the balance in 26 inches. I have included pictures and hopefully with those you can steer me towards which balances are the right ones to order.

Thank you for any help you can provide.

Tom

Thanks Bob. I measured my balance and compared it with the piece in the picture and it looks like a S-385-26. I'll order two so that I start fresh with both balances.

Tom