Which replacement parts?

Question

The brand name is Repco. We are looking to replace channel balances on four windows that are likely from the 1980s. The number on the metal part reads 29 C and 3.S.1, they are 30" long.

I can't figure out if we need this:
https://www.swisco.com/30-inch/pd/Series-351-Channel-Balances/S351-30

or this:
https://www.swisco.com/30-inch/pd/Series-390-Channel-Balances/S390-30

We probably also need these:
https://www.swisco.com/Take-Out-Clip/pd/Channel-Balance-Retainers/16-002

What seems right?

Thank you!

Bob · Accepted Answer

I agree you have either an S351-30 or S390-30. The difference between these two balances is the depth of the bottom nylon shoe, or 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. See the image below for reference. For a stamp option choose 2930.

Comparison of the S351 and S390 balance shoes.