This kit is in 1/700 scale. It is an add-on for existing Vietnam War era aircraft in the same scale. It is suitable for larger fighter aircraft such as the F-4, A-6 Intruder and so on.
The design is from the 300 Gallon Sargent Fletcher drop tank used by the US Navy. According to Wikipedia "In aviation, a drop tank (external tank, wing tank, or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in the event of emergency."