Containerization is the most vital factor of multimodal transportation as it combines the consistency of rail, flexibility of road, the cost effectiveness of shipping and speed of air transport. Container shipping is different from conventional shipping because it uses 'containers' of various standard sizes 20 feet (6.09m), 40 feet (12.18m), 45 feet (13.7m), 48 feet (14.6m) and 53 feet (16.15m) to load, transport, and unload goods. As a result, containers can be moved seamlessly between ships, trucks and trains. The two most important, and most commonly used sizes today, are the 20-feet and 40-feet lengths. The 20-feet container, referred to as a Twenty-foot Equivalent Unit (TEU) became the industry standard reference: so now cargo volume and vessel capacity are commonly measured in TEU. The 40-feet length container-literally 2 TEU -became known as the Forty-Feet Equivalent Unit (FEU) and is the most frequently used container today.