The picture is misleading. It shows a wheel that was machined. The actual wheel is made of sintered iron (looks like cast iron but it is easier to manufacture) and painted grey. It comes with all the pitfalls of chap casting, the major one being dimensional variability. There are more holes and smaller. The axle is bolt and nut - a plus because you can take it apart and add 10mm flat washers to stop the wheel moving from side to side. The bad part is that the wheel hole for the axle is not centered in the middle of the wheel and that the wheel hub side faces are not parallel to the wheel or to each other. So if you shim it with washers you will also have to clean the hub faces. Also the wheel hole for the axle is larger than the axle and even after shimming you will still get some side play. On the plus side is that the load is higher than the similar sized plastic wheels - the reason I bought them. You can also use more of them and mount them in a row to increase total load capacity while still maintaining maneuverability.