The 100mm Aluminum Mecanum Wheel Set (2 x Left, 2 x Right) includes 2 right wheels and 2 left wheels. Each wheel is composed of 9 rollers and can be driven independently. Mecanum wheels from Makeblock allow your robot to not only travel forward and backward, but also side to side. With 4 mecanum wheels, you can build a car/robot that can move in all direction. Each wheel of this pack comes with a compatible mounting hub - 4mm shaft connector, hence it will mate with our encoder motor or stepper motor easily.