Cooling Concepts 53-foot Step Deck Combo trailer is called a combo because the of the two different materials used in making the flatbed. The 120-inch upper deck is made of steel, and the lower deck is made with 1.25-inch aluminum. This is a reliable and sturdy flatbed that is ready for the long haul. Also, it is covered by our Fleet Service Center with roadside assistance, and our Back-Office support with keeping track of DOT and maintenance information.