YFROBOT Metal Mecanum wheels, 75mm in size, come in a set of four with couplings included.

Metal Mecanum wheel is a type of multidirectional wheel commonly used in robots and other automated equipment. It consists of a series of diagonally arranged wheels, usually made of metal.The design of the Metal Mecanum wheel enables it to achieve multidirectional movement, including forward, backward, lateral movement, and rotation. This multidirectional movement is achieved by changing the speed and direction of each wheel. When the wheels roll along a diagonal, they can produce lateral thrust to achieve lateral movement. When the wheels roll along their diameter, they can produce forward or backward thrust to achieve forward or backward movement.The advantages of the Metal Mecanum wheel are that it can perform precise movements in small spaces, while having high load-bearing capacity and long lifespan. These characteristics make it a widely used type of wheel in automated equipment and robots.

This link is for a 75mm(2.95 inches) Metal Mecanum wheels,They are available in four sizes: 60mm, 75mm, 100mm, and 127mm. Each set includes four wheels and four couplings, and is compatible with a variety of motor shafts ranging from 4-16mm in diameter.