Why continue to hassle with flat tires? Marathon flat free tires will never go flat but have the same bounce and flexibility of air tires. Constructed of lightweight solid polyurethane with a dense outer skin, they hold up to the bumps and bangs of yard work. They are unaffected by UV rays so you don't need to worry about cracking. Designed to fit most wheelbarrows on the market with 6-inch hub width and a 5/8-inch axle allowance.