Which window balance do I need?

Thank you for reaching out to us! Based on these photos, I recommend either the Series 380 or Series 385 channel balances. You'll have to measure the depth of the bottom shoe to see which Series is best for your repair.

If the metal channel measures 30", you may need the 2940 stamp option. A pair of balances with this stamp will support a sash weighing 23 to 28 pounds bit you can weigh your window sash on a scale to confirm. 

Comparison of the S380 and S385 balance shoes.