On trunks of different sizes can be 2 or 4 wheels and a pair of rollers bolee.2 suitable for flat surfaces. Their maneuverability allows the owner to exert minimum effort to move luggage. But due to the fact that the wheels protrude beyond the frame boundary, the risk of breakage increases. For not too smooth road approach road two-wheeled companion. However, mindful of the laws of physics, it is necessary to drive at an angle, taking the total weight of the luggage itself.