The cassettes are detachable steel platforms, which containers can be loaded on for transporting. The containers can be double-stacked so that either 2x40ft or 4x20ft containers can be moved. This is possible since the cassettes are able to handle 80 tonnes (there are examples of120-tonne versions used in thesteel industry).One of the advantages of using cassettes is that they act as a “floating” buffer, since containers can be placed on the cassettes with or without being coupled to a vehicle.