Shell material is made of injection molded polycarbonate, a highly impact-resistant plastic that is strong and lightweight. Four wheels, zero effort, four multidirectional spinner wheels allow 360 degree upright rolling in multiple directions so there is no weight on your arm. Provides easy maneuverability when extended out from the case, and stores neatly inside when not in use. Locks in place in both the fully extended and stored positions for secure traveling.