Bedroom windows 36 x 64 in

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Quick Learner from Southern California

Jul 1, 2026 3:53 pm

Replacing channel balances. Markings on balances are B.S.I 2720. Metal length is 28 in.

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2 Replies

Casey from SWISCO

Jul 10, 2026 9:05 am

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. Your balance appears to be stamped with 2730, which would correspond to 2730 spring strength options for your replacement balances. Thank you!

Comparison of the S351 and S390 balance shoes.