Extra Heavy-Duty Casters feature precision tapered thrust bearing with dust seal in lower raceway.Industrial Carts VideoBuilt from heavy plate steel with hardened bearings and sealed raceways for extra heavy load capacities. Equipped with a hardened 1″ king bolt welded to the top plate… Won’t stretch or break loose.Bearing seal keeps dirt out, while greasing purges old lube.Green epoxy powder coat finish.