Eliminate downtime! Marathon’s flat free 4.80/4.00-8-inch tire (15.5″ in diameter) is the perfect tire for contractor wheelbarrows. Airless tires have the same bounce, feel, cushioning, and performance as a regular air-filled tire. They are also non-marking and will not be affected by ozone or UV rays. Made of lightweight, solid polyurethane foam and guaranteed to never go flat. Mounted on an 8-Inch steel rim with a 6-inch centered hub and 5/8-inch ball bearings. Includes grease zerk.