The movable shelf is constructed of PP with white finish. 3-Tier open storage and 4 smooth casters make it the ideal small mobile cart. It has two tilted shelves that keep contents securely in the cart during transport and unobtrusive mobile storage solution.- Casters with locks: four 4'' swivel wheels, featuring better resistance to wear, allow easy movement in your workplace. Two of the wheels lock to keep the cart in place when not in use.-Versatile uses: you can feel at ease using in libraries, hallways, bookstores, classrooms, offices, meeting rooms, or any area that needs organization for essential files and books.