Appendix O to the FIA International Sporting Code defines the inspection and licensing process for auto racing circuits intending to host races sanctioned by the Fédération Internationale de l'Automobile (FIA), motorsport's governing body.
The grades are issued "with the sole purpose of permitting the registration of races on the FIA International Calendar, for the categories of vehicles specified".
"[1] As such, a Grade One certification is required to host events involving Formula One cars.
Circuits holding Grade Three certification may host events involving "Category II Automobiles with a weight/power ratio of between 2 and 3 kg/hp".
Circuits holding Grade Four certification may host events involving "Category I Automobiles.