Explanatory notes
… intended use (military, sporting, scientific, publicity, etc.). These comprise balloons , free or captive (i.e., … balloons of the following types, used in aeronautics or meteorology : (1) Sounding balloons . These are used to … may weigh up to 4,500 g, but their normal weight varies between 350 and 1,500 g. (2) Pilot balloons . These are …