A device for the serial ejection of at least two fluid components comprises a spacer (19) providing at least two states, i) a first state allowing a front piston (7) to be displaced forwards by action on a rear piston (17) while a fluid volume is retained in a rear chamber (5) and ii) a second state allowing the rear chamber to volumetrically shrink while fluid is transferred past (or through) the front piston thereby enabling the use of a liquid, initially provided in only the rear chamber, for the dual purposes of mixing and rinsing.
