Hello I need help ordering a balance spring for my window

I think we can help you with this. Have a look at both our S380-27 and S385-27 channel balances. The only difference between these two balances is the 'depth' measurement of the bottom balance shoe. You will need to measure the depth of your bottom shoe, like in the diagram below, to determine which of the two balances would make the better match. Whichever one chosen will use a 2630 option that supports a sash weight of 13-19 pounds. 

Alternate view of 15-004