Replacement sash balance

Thanks for posting. This looks like either an S380-30 or S385-30. The only difference between these two channel balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. See the diagram below for reference. In either case, choose 2930 as a stamp option.

Comparison of the S378, S380 and S385 balance shoes.