Traveler&rsquo;s Choice Silverwood Polycarbonate Hardside Expandable Spinner Luggage Case - Brush Metal  (21-Inch) Patent-pending dual cyclone spherical spinner wheel system provides wide wheel base for better traction and stability The wheels features a 5mm shock-resistant materials that assure smooth maneuverability and quiet rolling experience Each half of the dual cyclone wheel can move independently in the same or opposite direction, allowing you to roll or spin your suitcase effortlessly over uneven and smooth surfaces The four multi-directional dual cyclone wheels allow the suitcase to roll upright, so there's no weight on your arm or shoulder Expansion gusset boosts extra packing capacity by 2 inches up to 25%