Window Channel Balances

If the metal channel, not including the nylon fittings, is 15" long, then this appears to be a S350-15. The stamp code '15B' is pretty unusual for a balance of this size though; for non-tilt window channel balances, typically those first two digits is one number less than the actual balance length. It's possible these balances were cut down to size to fit your window. Either way, to know what stamp option to select, you'll need to obtain the exact weight of 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.