Known as "The World's Lightest Luggage Set," the XCase-XL is made of a durable blend of polycarbonate and ABS for rigidity and flexibility. These cases won't permanently deform when under pressure but will pop back into their original shape. The large, ball-bearing wheels are located on the outside edge of the luggage to provide greater stability and control when rolling over rough surfaces. The uprights' lightweight construction allows you to pack more items for flights.