The disclosure includes a flexible bag (1) intended to receive a biological fluid with a view to its centrifugation. The bag includes 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 fluid. The external enclosure (2) is provided with at least one inlet (6) and/or outlet (7) orifice for the fluid. The bag (1) also includes means (8) for the temporary association of at least one component with the bag (1). The means (8) is 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 component between the means (8) and the enclosure (2) so as to provide temporary association during the centrifugation of the bag (1).