ULCC refers to the largest oil tanker, larger than VLCC.

ULCC tankers are in the range of 320-560 dwt. They are used exclusively for crude shipping.

ULCC crude tankers are typically used on long haul routes. They can not go through the Panama or Suez canals. They are also draft limited in which ports they can enter. Frequently draft limits are avoided by lightering cargoes onto or off of ULCCs using smaller ships.