A 3D flexible pouch to be filled with a biopharmaceutical product , preferably by means of at least one flexible supply line (T1, T2), and provided with at least one connection port for filling and/or draining, the flexible pouch being designed to unfold from a flat configuration when empty to a substantially parallelepiped configuration in a filled state, the flexible pouch having: - a first wall element consisting of a film and allowing a front face to be defined, - a second wall element consisting of a film and allowing a rear face to be defined, - a first bellows and a second bellows , each connected to two lateral edges of one and the other of the first and second wall elements , the first bellows and the second bellows consisting of respective films cut in one piece and each able to fold toward the interior along a fold line (FL1, FL2) which extends between two opposite ends of the flexible pouch , and - said connection port , formed exclusively in one of the first wall element and the second wall element , the first wall element and the second wall element being welded together along a so-called transverse direction to one at least of the two opposite ends , wherein the first wall element and the second wall element have a given dimension (L2) along said transverse direction which is, at least in the flat configuration, substantially the same: - in said front and rear faces , - and at one at least of the two opposite ends , where a continuous weld extends over the totality of the given dimension (L2), Knowing that in the parallelepiped configuration: - the maximum extension of each of the first and second bellows is at least 15 cm between the first wall element and the second wall element ; and - the flexible pouch allows delimiting an interior space at least equal to 2L, said continuous weld also allowing, in the same end of the pouch, retaining, in a folded state, an edge portion of the first bellows and an edge portion of the second bellows , both in the flat configuration and in the parallelepiped configuration, characterized in that the material of the four films is identical. - a first wall element consisting of a film and allowing a front face to be defined, - a second wall element consisting of a film and allowing a rear face to be defined, - a first bellows and a second bellows , each connected to two lateral edges of one and the other of the first and second wall elements , the first bellows and the second bellows consisting of respective films cut in one piece and each able to fold toward the interior along a fold line (FL1, FL2) which extends between two opposite ends of the flexible pouch , and - said connection port , formed exclusively in one of the first wall element and the second wall element , the first wall element and the second wall element being welded together along a so-called transverse direction to one at least of the two opposite ends , - in said front and rear faces , - and at one at least of the two opposite ends , where a continuous weld extends over the totality of the given dimension (L2), - the maximum extension of each of the first and second bellows is at least 15 cm between the first wall element and the second wall element ; and - the flexible pouch allows delimiting an interior space at least equal to 2L, said continuous weld also allowing, in the same end of the pouch, retaining, in a folded state, an edge portion of the first bellows and an edge portion of the second bellows , both in the flat configuration and in the parallelepiped configuration, <EOS>