Abstract: The subject matter of the invention is a flexible bag (1) intended to receive a biological fluid with a view to its centrifugation, comprising an external enclosure (2) formed by two sheets of flexible plastic (3, 3′) connected at their periphery (4) so as to define an internal volume (5) for the said fluid, the said external enclosure (2) being provided with at least one inlet (6) and/or outlet (7) orifice for the fluid, the said bag (1) also comprising means (8) for the temporary association of at least one component with the said bag (1), the said means (8) being disposed on the external enclosure (2), in which the temporary association means are assembled on the bag (1) on a part of the periphery (4) of the enclosure (2) and are arranged to allow the insertion of the said component between the said means (8) and the said enclosure (2) so as to provide temporary association during the centrifugation of the bag (1).