They're made of industrial-grade steel with ball bearings and durable polyurethane (rubber-like) tread. They glide on the floor much more quietly than standard casters and with a lot less effort.

The casters are available in wheel diameters of 6 and 8 inches with either rubber-on-cast-iron or polyurethane-on-cast-iron wheel materials. The 6-in. wheels’ overall height is 7-3/4-in.; ...

While the rubber wheels cost twice the price of the standard polyurethane ones, Diaz said P&H Casters’ natural rubber wheels can last for about a decade, barring mistreatment from customers.