Bernd,
If you have visited the California Car Cover website (posted above by jockbolter50), you most likely have looked at
their cover selector. There are at least three key reasons you might want a car cover: paint protection, dust protection, and weather protection. Different types of fabrics and combinations of fabrics provide different qualities of service relative to the reason(s) you want the cover.
CCC is relatively expensive but they have good covers. You can get good quality covers from other vendors. Figure out what qualities you want and then shop around.
Tim