MARATHON 00003 3.50/2.50-8 FLAT FREE WHEELBARROW TIRE – RIBBED TREAD – 6″ CENTERED – 5/8″ BEARINGS OUR FLAT FREE TIRES ARE MADE OUT OF POLYURETHANE FOAM. THEY HAVE THE BOUNCE AND CUSHION OF AN AIR-FILLED TIRE BUT OFFER THE BENEFIT OF NO FLATS!! NOT FOR HIGHWAY USE.