YFROBOT Plastic Mecanum Wheels, 80mm in size, come in a set of four with couplings included

The Plastic Mecanum Wheel is a type of robot wheel typically made of plastic material, and its special design enables the robot to move in any direction on a horizontal plane, including translation and rotation. It is used for the movement of robots and vehicles. The Mecanum wheel has a special wheel rim with inclined small rollers, allowing the wheel to slide diagonally and laterally, rather than just moving in a straight line. The advantages of the Plastic Mecanum Wheel include being lightweight, low noise, easy to produce and use. They are commonly used in education, entertainment, and small-scale robot applications, such as robot soccer, unmanned vehicles, and automated navigation vehicles. However, compared to Metal Mecanum Wheels, the load-bearing capacity of Plastic Mecanum Wheels is lower, and may not be suitable for robot applications that require large loads or high-speed movement.

This link is for a 80mm(3.15 inches) Metal Mecanum wheels,hey are available in four sizes: 48mm, 60mm, 80mm, and 97mm. Each set includes four wheels and four couplings, and is compatible with a variety of motor shafts ranging from 3-6mm in diameter.