This medium duty caster wheels series combines 3 inch / 4 inch / 5 inch and even 6 inch wheels with 60 kg -150 kg load capacity,and different installation with Top plate / Threaded stem / Bolt hole / Inserted link casters and wheels,very popular for the platform trolley,hand cart etc. They are also called as trolley wheels since they are used with trolley carts, but the medium duty one. We also have many kind of different material for wheels, polyurethane, plastic, pvc, rubber, tpr, nylon etc. Depends on your desire. And we can customize color, logo, package for you too.