Flexi-bags (also called flexi-tanks) offer an alternative to ISO tank containers for shipping oils, juices, wines, food-grade liquids and nonhazardous chemicals across the globe. Flexi bags are usually loaded into 20' food-grade, ISO containers for maritime transport. Sizes range from 16,000 to 26,000 litres. For transport in the US, the materials used in the production of flexi-bags have to meet the US Food and Drug Administration, EU food-grade or German BAG standards. The idea is to isolate the liquid being transported from ambient air to avoid oxidation. 
It can also be used to transport base oils.
Depending on the product many ISO tank container operators argue that Flexi Bags can be more costly and less environmentally sound. This is generally the case for higher value products and/or environmentally dangerous products, because the transport protection offered by a Flexi-bag is less and the level of product that is left in the flexi-bag (2 to 5%) is higher than the amount left in a tank container.