Can I use a Series 390 for a lighter window?

A quick learner from FLORIDA says:
Does it matter if I use a 390 series balance designed for a heavier window on a lighter window. Also my top sash guide measures 1 9/16" in length. The closest I can find here is the 18-009 1 5/16" the rest of it measures the same. Will this be a adequate replacement? Thank you.
Profile picture of Paul
Paul from SWISCO responded:
The balance Series is determined by the balance fittings, not the strength of the balance. If you can make sure the top guide attachment on your balance matches the one on the Series 390, it should work as a replacement.
Profile picture of Donna
Donna from SWISCO responded:
As for the top sash guide, the 18-009 will work for you if the installation hole placement matches up to your original.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)
Current wait time is 4-7 business days
We promise that one of our experts will personally get back to you as soon as they are able. Thank you very much for your patience and understanding. If your inquiry is time-sensitive, please feel free to reach us at 856-317-6263 or at