Need a window channel balance replacement but need help determining size

A quick learner from Oakland, CA says:
August 28, 2015
I have a 33 inch window balance (1/2 inch width inside) that I need to replace - I would need at least four of these window channel balances. Attached are pictures showing the markings, and the top and bottom notches.
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
August 31, 2015
Thanks for posting. Please see our S385-33 channel balance. I believe this is a good match. As for the proper option, I recommend weighing your sash on a scale to determine what would be best. You can refer to the chart we have on the S385-33 store page.
A quick learner from Oakland CA says:
August 31, 2015
Paul: Thanks for your help. It is hard for me to weigh the sash -- I tried putting a bathroom scale underneath the window while it is still installed but it appears that i need to take the window out altogether to get an appropriate weight -- something that I just don't have the capacity to do. Is there a way I can mail a sample of the window balance so an appropriate match can be made.
Profile picture of Paul
Paul from SWISCO responded:
September 1, 2015
Unfortunately, being sent a sample of the balance will not allow us to determine the spring strength. The only way to know for sure is for you to weigh your sash. If you are unable to do so, you could possibly go with our 3265. Two balances with the 3265 option can hold a sash weight of 35 through 39 pounds, but this is just an educated guess. I cannot guarantee that it will work for you.

Removing the sash from the window frame is actually very simple. Check out this video, this should give you some idea on what you can do.
33" Series 385 Channel Balance
33" Series 385 Channel Balance
S385-33
$11.52
How to Replace a Non-Tilt Channel Balance
How to Replace a Non-Tilt Channel Balance
VIDEO
WATCH >
How to Repair a Jammed Window
How to Repair a Jammed Window
VIDEO
WATCH >
How to Identify Replacement Channel Balances
How to Identify Replacement Channel Balances
VIDEO
WATCH >
How to replace a non-tilt channel balance
How to replace a non-tilt channel balance
GUIDE
READ >
Choosing a Non-tilt Channel Balance: What Will We Need?
Choosing a Non-tilt Channel Balance: What Will We Need?
GUIDE
READ >
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 3-4 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 (888) 991-1929 or at help@swisco.com.