Eliminate downtime! Marathon flat free 4.80/4.00-8-inch tire is an airless, contractor-grade wheelbarrow tire with the same bounce, feel, cushioning, and performance as a regular air-filled tire. These non-marking tires are made of lightweight, solid polyurethane foam and are 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.