15.5" Diameter, Flat Free Contractor Wheelbarrow Tire, 4.80/4.00 - 8", Ribbed Tread, 15.5" Diameter, 6" Hub, 5/8" Ball Bearings, Solid, Lightweight Polyurethane Foam Tire Mounted On Steel Rim, Provides The Bounce & Feel Of Air Tires With The Benefit Of No Flats, Includes Grease Zerk.