Window balance size

A home owner from Madawaska Maine says:
August 19, 2023
I came to order a new window balance as one of mine is broken but I'm not sure the right size. My existing balance appears to 20.5 inches long with a tube diameter of about 0.5 inches. There was a pic tube which has rotted away of an unknown diameter over the spring. What do I need to replace this?
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Bob from SWISCO responded:
August 20, 2023

Thanks for posting. For a spiral balance that has a length ending in a X-1/2" increment, simply round up--so in your case, go with 21". Is the outer tube that has mostly broken away 5/8" in diameter? If so, go with a S600-21. Let me know if that diameter doesn't seem right. Let me know if you have further questions. 
21" Series 600 Spiral Tilt Window Balance
21" Series 600 Spiral Tilt Window Balance
S600-21
$8.58
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