Domestic construction material is (1) an unmanufactured construction material mined or produced in the U.S., or (2) a construction material manufactured in the U.S., if the cost of its components mined, produced, or manufactured in the U.S. exceeds 50 percent of the cost of all its components. The cost of each component includes transportation costs to the place of incorporation into the construction material and any applicable duty (whether or not a duty-free entry certificate is issued). Components of foreign origin of the same class or kind as those listed in Non-Available Products (subsection to this practices) are treated as domestic.