<p>A shut-off nozzle for the injection molding of fluid plastics. The nozzle includes an axial body component with a bore for transfer of the fluid plastic from the molding machine to the molding cavity through a nozzle head. The nozzle body carries thereon an actuating cylinder mechanism for selective actuation of a core plug and valve assembly. The valve is reciprocated to fully close or fully open a delivery bore in the nozzle head.</p>