channel balance

Hello,

It looks like you have either our S351-29, with a 15-002 bottom attachment, or S390-29, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need. Your stamp look like a (28 4) to me, which would be a 2840 spring strength option. To confirm, you can view the chart under the product description to choose an option based on the weight of your window sash. 

Also, keep in mind that we only measure the metal channel when determining length, which should make yours 29" long. Thank you!

Comparison of the S351 and S390 balance shoes.