Heavy-duty polyurethane on iron casters. Get the 1,250lb load capacity of cast iron with the quiet, floor-protective ride of polyurethane. Resistant to grease, oil, and chemicals. Perfect for industrial carts and machinery. High-Strength Core: The cast iron core prevents wheel deflection under extreme loads, while the polyurethane tread protects your floors. High-Visibility Red Tread Bearing Types: Precision Sealed Standard (Roller Bearings optional) All wheels are 2" wide 4"x 4.5" Top Plate High load capacity to 1,250lbs/each Quiet, shock-absorbing ride Floor Protection