A W420 steel ball wheel is a type of wheel that consists of a hub, a rim, and a number of steel balls that are arranged around the rim in a circular pattern. The steel balls serve as the wheel's bearings, allowing the wheel to rotate smoothly. W420 steel ball wheels are often used in applications where it is necessary to reduce friction and increase the smoothness of motion, such as in conveyor systems, material handling equipment, and other applications. They are made of high-strength steel and are able to withstand a high level of wear and tear. The size of a W420 steel ball wheel is typically specified by its diameter and width, and the size of the steel balls that are used in the wheel's bearing system is also typically specified.