6″ Wheel diameter Fixed caster 4-1/2″ X 4″ Plate 440 lb. Capacity Black rubber knobby wheel We call these are “all terrain” Caster for good reason. These solid rubber knobby tires on a steel hub with ball bearings are perfect for wet, uneven terrain or for surfaces littered with debris. They are great for use on lumber carts, and with some creativity can help make a great “off road” Tool hauler for those extended projects away from the shop. These 6″ Fixed casters have a 4-1/2″ X 4″ Plate and 440 lbs. Capacity. From the Manufacturer Red polyurethane tire is molded onto a tough hard rubber hub. Integral roller bearings in the hub make installation on an axle shaft quick and easy. Rounded profile of the tire delivers minimal rolling resistance, and the polyurethane material will not mar or scuff floor surfaces.