Window Channel Replacement

Thanks for posting. It looks like both nylon attachments lack 'wings', or side tabs. Please confirm. If so, you have either the S351-24 or S390-24. The only difference between these two channel balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both shoes with your old balance's to see what matches best. In either case, for a stamp option choose 2320. Let me know if you have any questions.

Comparison of the S351 and S390 balance shoes.

Thanks for getting back to me. It's unusual for a balance whose stamp has first two digits being '23' also being 23" long. Usually the balance is 1" longer. It's possible whoever installed these balances cut them down to size to fit your window. To get an accurate stamp option, weigh the window sash these balances support. Give me that exact weight, and I can work out what you need. 

If there are no wings on either end attachment, and the shoe is exactly 1" deep, then the Series 351 is correct.