6" x 3" Ultra-Poly Cast Wheel Swivel Caster - 2,400 lbs. capacity6" x 3" Polyon Cast Wheel Swivel Caster The Ultra Poly wheel is a higher capacity alternate to our standard Polyon Cast wheels. Boasting a 3 4" thick, non marking polyurethane tread and stronger cast iron core, this wheel provides a longer life under very heavy loads. Tread: 3 4" thick polyurethane elastomer Core: Heavy Duty Cast Iron Core Bearing: Roller Bearing Rig: Forged steel swivel caster, 4 1 2" x 6 1 4" mounting plate Capacity: 2,400 Lbs.