Abstract: A dual chamber injection system, comprising a guiding element arranged along a longitudinal axis and configured to at least partially contain a medicament container, the guiding element defines an inner surface and at least one protrusion extending radially inwardly therefrom; a plunger rod assembly, comprising a plunger outer portion arranged along the longitudinal axis and a plunger inner portion arranged concentrically within the plunger outer portion and having at least one guiding groove arranged on an outer surface of the plunger inner portion; the plunger outer portion is disposed externally relative to the guiding element; the plunger inner portion is at least partially received into the guiding element; and wherein the plunger rod assembly is displaceable relative to the guiding element and the displacement is guided by engagement of the at least one protrusion with the at least one guiding groove.