27 C channel

Hello,

It looks like you have either our S351-28, with a 15-002 bottom attachment, or S390-28, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need. You'll also need a 2730 spring strength option for your replacement balances, which will support a window sash between 13-19 lbs. Thank you!

Comparison of the S351 and S390 balance shoes.