It's just a spiral.
Apply a thick stroke with rounded caps. Then set the opacity of the stroke (and only the stroke) to 0
Then select knockout group for the object (also transparency panel).
See manual for details.
Oh and I forgot: apply a blue fill to the spiral.
Thanks for the quick help. But is it maby possible to take some printscreen.
i selected the spiral and apply the thick stroke with rounded caps. (opacity is 0)
i have no knockout group in the transparency panel..
ok i will try that tomorrow and i will let you know something.