2920 30" Chanel says "B.S.I."

Hello,

It looks like neither the top nor bottom attachment of your balance has wings. If that's the case, you have either our S351-30, with a 15-002 bottom attachment, or S390-30, 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 2920 spring strength option for your replacement balances. Thank you!

Comparison of the S351 and S390 balance shoes.