Since the 1970s most international freight has been shipped by standardized 20- and 40-foot containers. Some of this huge flow of cargo between countries needs to be refrigerated for the transit. The second most common type of ISO* container in use is the refrigerated container. Today's refrigerated container design uses high tech composite (plastics and metals) construction and a "picture frame" type refrigeration unit. Atlas' model represents a standard 40-foot high-cube refrigerated container (ISO Type Code 45R1) found in many shipping and leasing fleets.