BSI window balance

Thank you for sharing your photos with us. Take a look at both our S351-22 and S390-22 channel balance. The balances look exactly the same with the exception of the depth measurement of the bottom balance shoe. The depth measurement of the bottom shoe for the Series 351 is 1" and for the Series 390 is 1-1/8". Measure the depth of your bottom shoe, like in the diagram below, to determine which of the two balances is the better replacement for you. Whichever one chosen will go with the 2120 option that holds a sash weight of 8-12 pounds.