A biological fluid sampling system comprising: a biological fluid transfer device adapted to receive a multi-component blood sample, the biological fluid transfer device comprising: a housing having an inlet port and a transfer port, the inlet port and the transfer port in fluid communication; a mixing channel in fluid communication with the inlet port and the transfer port, and a blood separation element disposed between the inlet port and the transfer port, the blood separation element adapted to restrain a first component of the multi-component blood sample and allow a second component of the multi-component blood sample to pass therethrough, characterized in that the mixing channel is shaped to promote mixing of the multi-component blood sample; the biological fluid sampling system further comprises: a first interface removably connectable to the inlet port of the biological fluid transfer device, the first interface- configured for connection to a first biological fluid collection device; a second interface removably connectable to the inlet port of the biological fluid transfer device, the second interface configured for connection to a second biological fluid collection device; and a packaging member having a compartment (40, 42, 44) sized and adapted to receive the biological fluid transfer device, the first interface, and the second interface therein, wherein the first interface is different from the second interface. a biological fluid transfer device adapted to receive a multi-component blood sample, the biological fluid transfer device comprising: a housing having an inlet port and a transfer port, the inlet port and the transfer port in fluid communication; a mixing channel in fluid communication with the inlet port and the transfer port, and a blood separation element disposed between the inlet port and the transfer port, the blood separation element adapted to restrain a first component of the multi-component blood sample and allow a second component of the multi-component blood sample to pass therethrough, a housing having an inlet port and a transfer port, the inlet port and the transfer port in fluid communication; a mixing channel in fluid communication with the inlet port and the transfer port, and a blood separation element disposed between the inlet port and the transfer port, the blood separation element adapted to restrain a first component of the multi-component blood sample and allow a second component of the multi-component blood sample to pass therethrough, characterized in that the mixing channel is shaped to promote mixing of the multi-component blood sample; the biological fluid sampling system further comprises: a first interface removably connectable to the inlet port of the biological fluid transfer device, the first interface- configured for connection to a first biological fluid collection device; a second interface removably connectable to the inlet port of the biological fluid transfer device, the second interface configured for connection to a second biological fluid collection device; and a packaging member having a compartment (40, 42, 44) sized and adapted to receive the biological fluid transfer device, the first interface, and the second interface therein, wherein the first interface is different from the second interface. a first interface removably connectable to the inlet port of the biological fluid transfer device, the first interface- configured for connection to a first biological fluid collection device; a second interface removably connectable to the inlet port of the biological fluid transfer device, the second interface configured for connection to a second biological fluid collection device; and a packaging member having a compartment (40, 42, 44) sized and adapted to receive the biological fluid transfer device, the first interface, and the second interface therein, wherein the first interface is different from the second interface.