A syringe for storing and delivering a fluid that includes (1) a stopper and (2) a plunger rod assembly is provided. The plunger rod assembly includes a plunger rod and a threaded member at a plunger-engaging end. The stopper may be formed of an elastomeric material. The stopper has an exterior surface and an inner cavity. The inner cavity of the stopper may have a generally frustoconical shape with at least one engagement surface. The threaded member contacts at least one engagement surface in the inner cavity of the stopper to support the plunger rod assembly in an integrated, non-threaded engagement with the stopper. In some embodiments, the threaded member is freely rotatable within the inner cavity.