This is a 34cm round pot trolley made from cast aluminium and powder coated satin black with clear polyurethane wheels (no scratching/marking).
The trolley base itself has raised edges to keep the pot from slipping off. It's very rugged and can hold 100kg+ of weight and still remain mobile. The aluminium material used has been chosen for its weather resistance so there will be no issue even after years of use. The picture of the trolley with the plant on it is from my own house, that pot is ~40kg in weight.