Wheel diameter: 50mm. Set comes with 4 swivel castors with brakes. Material: Rubber wheel, Heavy-duty steel plate. Rotation: 360 degrees, durable, quiet, leaves no trace. Ideal for DIY to industrial applications, garden, home, schools, garage, trolleys, etc. Load capacity: 400kg, each role carries 100kg, 400kg in total. Note: The data are all measured manually, please allow 1-3cm error, due to the difference in light and display, there will be a certain color difference, the actual object received shall prevail.