The wheels are a 2″ blade type wheel, this is important as I have found the standard “office chair” castor wheel if left outdoors will over time seize and crumble if the weight of the pot is more than 30kg. This wheel, I specifically searched for can handle a large amount of weight, be weather resistant and still work in a years time where the other office wheels have already stopped working. They do cost a bit more but in the long run they are much better if you do plan on moving the pots in and out of the sun & water.
The other advantage of having a clear polyurethane wheel is that it allows you to use the pot trolley indoors without having to worry about scratching your tiles or polished concrete flooring.
Please note the trolley is packaged unassembled to make shipping easier, when receiving the parts you simply need to lightly tap the wheel into the holes on the underneath of the casting.