How to choose the size: Ordinary Car: 5 meters for 4 doors vertical edge 8 meters for 4 doors vertical edge+bottom horizontal side 13 meters for 4 doors vertical edge+bottom horizontal side+bottom side of the trunk Off-road Vehicle SUV: 5 meters for 4 doors; 8 meters for 4 doors+bottom side of the trunk 10 meters for 4 doors+bottom side of the trunk+the hood