Series 390 Channel Balance

if your stamping states that it is "16" then that tells us that the metal length measurement of the balance should measure 17" in length. It's best to remeasure the metal length portion of the metal balance only to confirm that it measures 17" in length. If so, then you will go with the S390-17 with a 1620 option.

Hmm.. Could we have you send us a photo of the channel balance alongside a tape measure where it shows the metal length only being 16" long? There are times when the original window installers have installed the incorrect type of balance, so we want to see if that is the case here or if we can rule that out and explore other reasons on why this could be on the peculiar side. 

Ah, so it does in fact look like the top of the metal balance channel was cut down to 16". In this case go with Series 390-16 with a 1520 option.