WHEEL MATERIAL: Polyurethane Solid. the wheel and the core is one mold - Makes it super heavy duty, an Amazing 500LB Capacity Per Wheel. QUALITY : These caster wheels are made of precision molded solid polyurethane. These polyurethane wheels offer easy roll-ability, floor protection, non-marking and non-conductive performance. Polyurethane resists most chemicals, oils and rejects floor debris. Our industrial wheels are ready for your heavy duty project. FEATURES: These Low Profile Caster Wheels give you the ability to Carry items of very heavy capacity while staying low profile. HEAVY DUTY BEARINGS: Steel structures body is extremely hard wearing and resistant to dirt, Bearing Heavy Duty.