This 4" x 2" Polyurethane Ergonomic wheel is a high quality polurethane wheel that has a donut tread. This is an great choice to (1) prevent user injuries by reducing push/pull forces, (2) maintaining a quiet environment, (3) preserve flooring by dispelling debris, (4) be non-marking, (5) be strong and durable, and (6) carry significant weight loads.