Window sash?

Thanks for posting. I believe the nylon attachments on both ends lack 'wings', or side tabs, is that correct? See the image below as reference.

Diagram on how to choose between the 15-001, 15-002, 15-004, and 15-005 channel balance shoes.

If both fittings do lack wings, then this is either an S351-29 or S390-29. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both with your old balance to see what matches best. For a new stamp option choose 2810.

Comparison of the S351 and S390 balance shoes.

Excellent! Let us know if you have any other questions, and many thanks for reaching out.