The wheels were constructed like chariot wheels; their crossbars, rims, spokes, and hubs were made of cast metal.
Referenced Verses
Ezek 1:16 : 16 The appearance of the wheels and their construction was like gleaming jasper, and all four wheels looked alike. Their structure was like a wheel within a wheel.
Ezek 1:18 : 18 Their rims were high and awesome, and the rims of all four wheels were full of eyes all around.