extended spiral balance - old non-tilt aluminum windows

A quick learner from Florida says:
I think I have extended spiral balances.
One window has metal rods which are approx. 28.5" and the spiral rod is 30.75".
The other window has a metal rod approx. 16.5" and its rod is 18.75". They are 3/8" in diameter and the holes in the spiral rod at the bottom are 1/2" apart. Do you sell these?

Also, I understand the metal clips are obsolete. Are they necessary for the operation of the window? Is there an alternative?
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Paul from SWISCO responded:

Many thanks for writing in. You are correct about the metal fork; it hasn't been available since the 1970's. The function of the forks are to hold the nylon shoe in place so to make it easier to install the sash. It doesn't have any function on the sash performance. As for the 3/8" balance tubes with extra long spirals, they are our Series 300 balances. 

Now, we need to find out what nylon shoe is that you need to attach to the spiral. Since they are missing on your old balances, please show us the top and nylon fittings on the side of the sashes. They might help us to determine what nylon shoe you need on the spirals. Many thanks.

A quick learner from Florida says:
I'm finally back on this project...sorry for delay! Attached are a couple pictures of an old shoe from one of these windows. Can you tell which part that is? I have 12 windows that need these parts, but I think I should start with one first to make sure I am getting the correct parts. Thank you for your response.
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Bob from SWISCO responded:

Hello again! Perfect, these photos confirm you had Series 300 Spiral Balances with the 15-020 Shoe Attached. We'd be happy to make these up for you via a custom order. Earlier you indicated to us you had one window with 28-1/2" long balances, and another with 16-1/2" long balances. This equates to our 29" and 17" long balances, respectively. I am sending you an email with two custom link to order the 17" pair to start with. Let us know if you have any other questions. Also, note that you should check your bottom sash guides to see if they are broken or not. 

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