Milgard channel balance.
A contractor from Hendersonville, NC says:
July 5, 2016
I'm trying to determine what is the right channel balance to order for a clients circa 1985 Milgard windows. The measure 21" L 9/16" length and the only stamp on them is 20 C. See attached photos.
Paul from SWISCO responded:
July 7, 2016
Please see our S390-21 balance and carefully compare it to your own hardware. I think this may match, but I would just look over our information to be sure. As for the option, I would recommend the 2030 based on your stamp of "20 C."