Correct Spiral Balance for Alcoa Window

A quick learner from Ohio says:
Can you help me determine the correct spiral balance?
Mine appear to measure 28.5". They are 3/8" in diameter. They are metal covered with plastic. They have blue balance tips.
I am attaching some pictures.
user submitted photo of spiral balances
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Donna from SWISCO responded:
Before we provide you with a replacement balance option I want you to double check a couple measurements.

Recheck the diameter. You reported 3/8", but did you measure the diameter of the overall plastic tube? The S900 is 3/8", but the more popular S600 has a 9/16" (considered 5/8" in the trade). I just want to double check that you do indeed have the skinnier balance tube.

Usually the length of the balance tube will end on the inch (not the half inch like you reported). I see that your balances are in pretty bad shape which may make it hard to measure. Please provide the measurement of just the plastic tube and the measurement of the actual spiral removed from the tube. We can figure out which length you will need from those two measurements.
A quick learner says:
Thank you for your response!
I was just measuring the diameter of the metal tube inside the plastic cover. The diameter of the outer plastic layer is 9/16".

The length of the plastic tube is: 28 3/4"
The length of the removed spiral is: 29 3/4". That is tip to tip and includes the part of the spiral that goes through the blue bushing.
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Donna from SWISCO responded:
The closest balance we have to your dimensions is SWISCO balance Series 600; the 29" tube has an internal spiral that measures 30"; there is a blue tip option.
Here is a product link to get you started:

29" Series 600
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