RWM urethane on iron wheels are liquid cast and chemically bonded to our machined cast iron cores. The core is a heavy-duty solid web design with an oversized hub, enabling it to be machined to be fitted for special bearings or a keyway. Careful attention is made during the bonding process to assure that each urethane on iron wheel meets or exceeds RWM'sâ¬â¢s high standards of performance. They will outlast rubber wheels. In addition, these wheels are non-marking to floors and provide a more quiet ride than hard tread or steel wheels. Urethane wheels also provide outstanding abrasion resistance and are resistant to most chemicals, grease, oils and water. Our Premium PTMEG urethane provides longer service life, better wear and tear characteristics and rejects floor debris. All wheels up to 8" x 2-1/2" wide are standard crown tread that reduces the amount of friction between the tread and the floor, improving the roll ability and maneuverability of the wheel.