S380-34

Thanks for writing in. Channel balance length is determined by the length of the metal channel, not including the nylon fittings on either end. Typically, the first two digits of the stamp code are one number less than the length. So yes, a balance stamped 3330 is normally 34" long, and a balance stamped 2830 is normally 29" long. 

Sometimes, however, there's exceptions here, where the channel length will be shorter than what the stamp option indicates. This can happen, for instance, if a contractor working on a house cuts a balance down a little to fit a window it won't fit otherwise. That's why it's always best to check the length just to be safe. 

If your balances are indeed not 34" and 29" long, then see our Return Policy here. I recommend you confirm the metal channel lengths of these balances to know what length to select. The problem then is that your old stamp codes aren't reliable for picking a new stamp option, since they were designated for a different length. Obtain the exact weight of the window sashes that use these balances. You can then match those exact weights with the weight ranges listed alongside each stamp option on the balance shop pages.