Abstract: It comprises an envelope (1), a couple of independent air chambers (2,3), separated from each other by an inner partition (4) and arranged within the aforementioned envelope (1), an inflating device (5), and a box (6) made up of two complementary members (7,8) joined to the envelope (1).The inner chamber (3) communicates with the outer chamber (2) through a one-way valve (9), so that the inner chamber (3) stays inflated even if the outer chamber (2) accidentally deflates.The chambers (2,3) are divided into compartments (10) separated by partitions (11) pierced by small passage holes (12) to obtain a slow deflation in case of accidental leaks.The outer chambers (2,3) are provided with respective valves (13,14) with an important passage section to obtain quick deflation.The space occupied in transportation is reduced and blows are cushioned, by maintaining a high safety level. It incorporates the same inflating device (5).