The product is a set of 4 vintage industrial swivel caster wheels, made of steel and rubber. These caster wheels are rubber and have a classic industrial style and are designed for easy mobility with their swivel feature. Perfect for adding a vintage touch to furniture or salvaged pieces, these caster wheels are both functional and decorative. They appear to have a layer of rubber the help cushion any vibrations. The wheels are 4” across, the base measures 4"x 31/2" and the unit is 4 1/2" tall. Please email me if you have any questions.