West Coast Corvette's Ultra Guard Plus car cover is made of a 300 Denier polyester material with a water resistant coating on the outer layer and a soft cotton layer on the inside. Competitor's covers are only 210D! Our 300D Thickness cannot be beat. It's a great choice for all around indoor and outdoor use. The 300 denier is a very durable, strong, heavy weave, which will not rip or tear easily and holds up better over time. It does an excellent job of reflecting sunlight, while keeping rain and animal droppings from damaging the vehicle finish. The special soft cotton inner layer protects the most delicate paint finishes.