A mixing system (1) adapted to allow first contents of a first container (2) and second contents of a second container (3) to mix to form a material. The mixed material is retrieved to a syringe (20) without being foamed. The mixing system (1) comprises a transfer unit (5) which is adapted to receive the first container (2) at a first port (11), the second container (3) at a second port (12) and the syringe (20) at a third port (13). The transfer unit (5) further houses a number of fluid pathways (14, 15, 16) interconnecting the three ports (11, 12, 13) as well as a number of flow control members (17, 18, 19, 22) for controlling fluid flow between the containers (2, 3) and the syringe (20). At least one of the flow control members (17, 18, 19, 22) allows a user to switch between two states of fluid flow, one in which fluid flow is enabled between the first port (11) and the third port (13) as well as between the third port (13) and the second port (12), and one in which fluid flow is enabled between the second port (12) and the third port (13). The invention also relates to a transfer unit comprising first and second ports for receiving first and second containers, respectively, a third port for coupling to a syringe, a number of fluid pathways interconnecting the ports, at least one flow control member which allows a user to switch between two states of fluid flow, and a locking means to ensure that the at least one flow control member can only be manipulated when a syringe is coupled to the third port.