6" x 2-1/2" Energy Saver Polyon Kingpinless Swivel Caster - 1700 lbs. Cap.6" x 2 1 2" Energy Saver Polyon Wheel Kingpinless Swivel Caster Crowned polyurethane elastomer tread chemically bonded to a solid heavy duty cast iron core. Combination of crowned tread and heavy core, offers higher weight capacities, durability and greater mobility than standard Polyon wheels. Tread: Polyurethane elastomer tread chemically bonded to cast iron core Core: Heavy Duty Cast Iron Bearing: Roller Bearing Rig: Forged steel swivel caster with