window balances

Thanks for your photos. Based on what I see here, you have either our Series 351 or Series 390, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

Comparison of the S351 and S390 balance shoes.

I think a 15-001 that has worn down is far more likely. This is actually pretty common for these kind of balances. Time and friction usually always wears the shoe down to be a little less than it once was.

Given your measurement, I think the Series 390 is a very safe bet.