Deep sea vessels or mother vessels as they are called, only call at a few limited ports and cargo is accumulated at these ports by feeder service from other ports of the region, Feeder ships are small size vessels of around 300/400 TEUs. These feeder ships transfer the container to deep sea or mother ships at specified ports. As for example, Singapore, Colombo and Madras have been serving as feeder ports where mother ships receive containers from feeder ships of the region.