Channel Balance

Thanks for posting. Hm, usually a channel balance with a stamp of 1810 would be 19" long. However, judging from your picture this certainly looks like it's only 18" in length. Sometimes whoever originally installed the window had limited supplies to work with, and thus they cut balances down to fit what they need. That's probably what happened here. 

The long and short of it is, if the balance is indeed 18" long, then it is either a S351-18 or S390-18. The only difference between these two balances is the 'depth' of the bottom nylon shoe, so compare both with your old balance to see what matches best. Once you know what balance to select, you'll need to choose a stamp option. Now, we can't necessarily rely on your stamp code of 1810, since this balance has been modified. I advise you weigh your window sash. You can then match that exact weight with one of the weight ranges listed alongside each stamp option on the balance product page. Let us know if you have any questions.