Featuring a green polyurethane tread and a silver cast iron core, this keyed drive wheel comes with a 20mm plain bore and a 6mm x 2. The non-marking and non-sparking tread protects floors, rolls quiet and is resistant to most chemicals, while the high capacity load bearing wears like iron. Service Caster’s polyurethane tread is liquid cast and chemically bonded to a Class 30 solid web cast iron center. Finally, featuring a 90-95 Shore (A) durometer, this wheel is a great option for anyone looking for a keyed drive wheel.