There seems to be a sweet tightening of the casters and the nut may come off. We reinstalled it again at the time of assembly. Please firmly tighten the nut of the caster the first time at the manufacturer.
Since size can be adjusted, it can be used properly according to the application. Assembly is very easy if you get used to it so quickly, but it is a little hard to tighten the tool to tighten the nut that was in the tool as a tool.