Sash Window Channel Balance Identification/Replacement

Question

Hello there! I have one side of a double hung sash with a busted balance assembly. The window sash is 22.9 lbs in weight.
The balance has the following printed on it: 26 4 KV CMC 9
Pictures attached!

PS- Is it recommended to but these in pairs, or can I just replace the broken one?

Thanks in advance for the help.

-Curtis

Tom · Accepted Answer

Hey, Curtis. Always change balances on both sides.

I think this is S385-27, but please verify. You should have the 1-3/32" bottom shoe shown below. If not, let me know. "2640" is the stamp option you'll want to choose.

Alternate view of 15-004