Window Balance springs

A home owner from San Diego, CA says:

need 2 sizes pics are side by side

#1 is marked 30 4 BSI NL, length is 31", window weight is 28 lbs

#2 is marked 27 4 BSI OD, length is 28", window weight is 18 lbs

PLease recommend replacement part numbers.

User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 380 or our Series 385 balances.

Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 380 uses the 15-005 while the Series 385 uses the 15-004. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.
15-004 and 15-005
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)