If you're unfamiliar with mecanum wheels, this Matching Left & Right pack of 48mm Diameter Mecanum Wheels may resemble everyday chunky wheels Frankenstein'd out of mini hair curler rollers. In reality, they are very cool, omnidirectional wheels with rollers that are supported by ball-bearings, allowing a four-wheeled robot to move in any direction. There are nine rubber beads around the perimeter of each wheel that lets it grip the floor when moving sideways.