An injection device having a first sub-assembly comprises a housing and a chamber. The chamber is disposed within the housing and has proximal and distal ends, an inner surface and an exit aperture. The sub-assembly comprises a stopper movably disposed within the chamber. The stopper has an outer surface substantially in contact with the inner surface about its perimeter. The sub-assembly comprises a port adapted to receive a container containing a fluid. The stopper is fixed with respect to the housing and movement of the port causes movement of the exit aperture in relation to the stopper.
