Flexible tanks (also flexi-bags, flexibags and flexi-tanks) are a kind of storage equipment for liquids such as water or oil. Compared to steel tanks, flexible tanks have many advantages, including lighter weight and being rustproof, foldable, and quicker and easier to set up. With the same capacity, an empty flexible tank may have just 10% of a steel tank's weight. The disadvantages of flexible tanks include lower durability and shorter longevity. Some flexible tanks can be used as transport containers on trucks, ships, or aeroplanes, with some suitable for use in airdrops, helicopter swing, or hauling water.
Flexible tanks can be made of high-tensile strength polyester fabric, with elastomer or plastomer (PU, PVC, nitrile) coated on both sides.