The 203mm Stainless Steel Mecanum wheel is a heavy Duty wheel. This (8 inch) 203mm Stainless Steel Mecanum wheel includes 2 Left and 2 Right wheels. Each wheel is comprised of 12 polyurethane rollers, these rollers have an axis of rotation at 45 to the plat of the wheel in a plane parallel to the axis of rotation of the wheel. As the wheels rotate in sync, the vehicle moves forwards or backwards normally, but by spinning pairs of wheels in opposite directions, the rollers enable sideways movement. put it all together, and you can move laterally, diagonally, or spin in a circle.