CasterHQ's flat free foam filled wheels are great alternatives to pneumatic tires since they cant lose air. Our flat free tires are filled with a micro-cellular polyurethane foam which provides a very light weight tire in return. These wheels have a wide foot-print like the pneumatic wheel. Our flat free wheels offer great durability and floor protection with no maintenance required. Comes with a 1-piece style gray metal hub and precision bearings. Choose your bearing size on the product page options. Questions? Call us at 844-435-4335 or email us here.