fixed top window but tilt-in bottomwindow needing spiral balance springs

A quick learner from Milton, DE 19968, USA says:
window:27x34x1.5inches 15lb. replacement needed: 26x3/8 inches
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Bob from SWISCO responded:

I am confident we can help, but the best way to know what you need is to remove one of the old spiral balances and show us. We need to know the length and diameter of the outer tube (not including the colored tip), and a picture of the color tip would be useful as well. From there we'll do our best to narrow down what you need.

A quick learner from Milton, DE 19968, USA says:
in response to your request for more info.... in my original email, i stated that the length needed is 26" and the diameter three/eighth inches... i dont understand what else is needed.. SPIRAL BALANCED....
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Bob from SWISCO responded:

My deepest apologies, I missed this information in your original statement. It sounds like you need an S900-26. For a sash that weighs 15 lbs, a Red Tip option will work just fine.

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