I put a 2000 pound milling machine on a set of these. They roll great considering the weight they are supporting. The machine can be turned, pushed and pulled anywhere on a relatively smooth concrete floor.
The only issue I have with them is the thumb wheel will not turn under a heavy load. In my case it was easy enough to put a floor jack under the mill and lift it up until the thumb wheel turned easily. It took a few back and forth sessions from side to side to get everything level but now the weight is supported by the foot and not the roller. I am sure the roller would develop a flat spot if they were left supporting that much weight. This way they will be nice and round when I need to move the machine.