First, the con. Order arrived with with plate mount instead of stud mount. Seller was VERY responsive, offered a discount if I wanted to keep them, which I did (used them on another project). I installed these under a 600 lb lathe which now rolls around very easily yet I can make it stationary in just a minute. The casters show no wear from the concrete and do not pick up debris from the floor. Leveling is another matter, there is no way you could level 551 lbs per caster without lifting the load with a pry bar. Though once leveled they do hold the load. I now also have these under my bench grinder stand and the lighter version under the wood shaper and jointer. I highly recommend these for the small shop that needs tool portability.
C. Freeman 
