Intermodal containers exist in many types and a number of standardized sizes, but the majority of the global container fleet are dry freight or general purpose containers, durable closed steel boxes, mostly of either 20- or 40-foot standard length. The common height is 8 feet 6 inches and 8 feet wide. These containers can carry a gross maximum weight of 66,139 pounds. Empty, the 20-foot containers weigh 4,850 pounds, while 40-foot containers weigh 8,380 pounds.
There are also 40- and 45-foot high-cube containers, whose dimensions vary. These containers are 9 feet 6 inches in height and 8 feet wide. The 40-foot high-cube container can carry a gross maximum weight of 68,008, while the 45-foot high-cube container can carry a gross maximum weight of 66,139 pounds.
Intermodal containers conform to ISO 668, which is an international standard which classifies intermodal freight shipping containers and standardizes their size and weight specifications. Introduced in 1968, ISO 668 regulates both external and internal dimensions of containers, as well as the minimum door opening size, where applicable. It also specifies the associated gross weight ratings, and requirements for load transfer areas in the base structures of containers.
Intermodal containers are sold and rented to clients as storage units. These include car dealerships, construction companies, event companies and those in the mining and forestry industry.