Heavy Duty Steel Wheels are made of heat treatable high carbon steel which increases wheel life. Our Wheels are plated to protect against corrosion and wear. They are designed with black lubricated nylon bushing, which acts as a bearing. Inside our nylon bushings is a bronze oilite bushing which created a dual lubrication system. This dual lubrication system never needs greasing on the sealed steel ball bearings. This is the the best option for heavy duty gate systems.