Sprial Balance for MW Window

Thanks for posting! It does sound like our S900-34 is the replacement you'll need for your existing tube. Although, you'll want to double check that you measurement up to the colored plastic tip, but not including it.

Since your balance has a white tip and you believe it is 20lbs, then the white tip option should work fine for your sash. It can support a sash weighing between 7 to 22lbs.