Single Hung Balancers

Thanks for posting. Please double-check the length. Measure only the metal channel; do not include the end attachments in this measurement. I believe you'll find the length to be 30". If so, these look like either our S380-30 or S385-30 channel balances. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. Compare both with your old hardware to see what matches. Use the illustration below for reference.

Comparison of the S378, S380 and S385 balance shoes.

You'll then need to choose stamp options, which designate the strength of the balance. The stamp of 29C conforms to our stamp option of 2930, which denotes a balance that can support a window sash in the weight range of 16 through 23 pounds; the stamp of 29-D conforms to our stamp of 2940, which designates a balance that can handle a weight range of 23 through 28 pounds. Were these balances from the same window, or are they from different ones? If they're from the same window, I'd highly advise obtaining the exact weight of the window sash to determine which stamp option would be best--you want the stamp options to be the same with both balances in the window. Let me know if you have further questions. 

Perfect, sounds like a plan. Best of luck with the rest of this project and please feel free to reach out if you needed anything else.