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 isretained in a rear chamber (5) and ii) a second state allowing the rear chamberto volumetrically shrink while fluid is transferred past (or through) the frontpiston thereby enabling the use of a liquid, initially provided in only the rearchamber, for the dual purposes of mixing and rinsing.
