Sash Balance Size?

A quick learner from Cincinnati, Ohio says:
Bought a house which was a flip of a flip. While trying to repair this double hung window (will have others to follow) it looks like I've come across a sash balance that has been cobbled together with pieces. The tube itself is 28 inches long with a 5/8" diameter, but the spiral itself fits completely inside of the tube with a blue tip. The outer (top) window may have a 25 inch tube. We've already purchased a 3/8 tube at 28 inches, but when installed, the window couldn't completely close. Help?
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Bob from SWISCO responded:

The diameter of the outer tube is what counts here. If it's 5/8", then it sounds like you need an S600-28 Spiral Balance. This comes with a Blue Tip option. Let me know if you have any other questions. 

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