Not sure if these are S390-30 or S350-30

Hey there,

Thanks for reaching out! Your balances are assembled with wingless top and bottom attachments like either the S351-30 or S390-30 channel balances. It appears you shoe measures closer to 1-1/8" so you'll likely need the S390-30. 

You'll need the 2930 stamp option. 

It would be advised to replace both balances at once. The older balance can cause the new balance to wear out much faster than it should. It may also be a good idea to double check the top sash guides at the top left and right corner of the window sash for any damage.

Comparison of the S351 and S390 balance shoes.

It sounds like you could have a broken top sash guide, which is used to hold the balance in place below the sash. There's a good chance that we can supply them but we would need to see an intact guide removed from one of your windows. See the videos below to assist you.