A device is disclosed for the serial ejection of at least two fluid components. The device comprises a barrel (1), a movable front piston (7) in the barrel defining a front chamber (3) and a movable rear piston (17) defining a rear chamber (5). A rear bypass arrangement (9) allows fluid transfer from the rear chamber (5) to the front chamber (3) and a front bypass arrangement (11) allows fluid transfer past (or through) the front piston (7) to the outlet (25). The device also comprises a spacer (19) that changes shape between at least two states. The first state allows the front piston (7) to be displaced forwards by the rear piston (17) while a retaining a fluid volume in the rear chamber (5). In the second state the rear chamber (5) can volumetrically shrink while fluid is transferred past (or through) the front piston (7). The device allows the use of a liquid (23), initially provided in the rear chamber, for both mixing and rinsing.
