Made of solid polyurethane, this tire has the same bounce, feel, and cushioning as a regular airfilled tire with the benefit of never going flat Nonmarking, polyurethane will also not be affected by ozone or UV Rays, Outside Tire Diameter: 8, Diameter of Tire and Caster: 10, Caster is 4x4, 5, Not for Highway Use, SKU: MTNI022