Abstract: A prefilled syringe including a vial containing a measured quantity of an injectable product is provided Adjacent an end the vial is a displaceable wall adapted to be urged by plunger means so as to expel the product from the vial through a needle. The syringe also includes a two part housing for the vial and the plunger. One of the housing parts includes a stop surface that cooperates with a pair of corresponding surfaces extending from an external surface of the plunger. The plunger stop surfaces are positioned on opposite sides of the housing part stop surface to limit the displacement of the plunger within the vial. The position of the stop surfaces on the plunger relative to the vial may be varied by rotating the threadably connected housing parts relative to each other. A click-stop mechanism provided with the housing parts permits the housing parts to be rotated relative to each other in predetermined increments. A graduated dosing ring may be rotatably mounted about the housing parts.