I mounted a commercial radial arm saw on these casters and it rolls well even over power cords or other small objects.  The saw and stand weighs about two hundred pounds and these casters handle it like nothing.  The only negative thing i have to say is that the spindle lock is very stiff the first few times you use them, it can take a lot of kicking the first few times to unlock the caster.  Ive had them about six months and have yet to have any problems with the polyurethane wheel deteriorating.