Are you looking for improved rollability and extra capacity in a resilient tread wheel? If so, Hamilton's 70 durometer polyurethane (Shore D) wheels will deliver. Because the polyurethane is harder than standard 95A poly, these wheels roll more easily and carry up to 30% more capacity - thus the suffix XC, as in eXtra Capacity! In addition, they effectively repel foreign objects and debris. Duralast XC's harder tread is best suited for smooth floors. For rough floors, we recommend our Ergo-Glide™ Wheels.