A handy person from michigan says:
June 8, 2014
my spiral balance color is white 5/8 38" should I buy the red or the black. I didn't weight the window.
Tom from SWISCO responded:
June 9, 2014
I can't say for sure. You should weigh your window sash just to be sure. You can compare that weight to the chart we show for the S600-38.