An intermodal container (also known as a container, freight container, ISO container, shipping container, hi-cube container, box, sea container, container van) is a standardized reusable steel box. Intermodal containers are used to store and move materials and products efficiently and securely in the global containerized intermodal freight transport system. "Intermodal" indicates that the container can be used across various modes of transport, (from ship to rail to truck) without unloading and reloading its contents. Lengths of containers, which each have a unique ISO 6346 reporting mark, vary from 8 to 56 feet (2.438 to 17.069 m) and heights from 8 feet (2.438 m) to 9 feet 6 inches (2.896 m). There are about 17 million intermodal containers in the world of varying types to suit different cargoes.