Abstract: An extruder assembly for an injecting moulding machine in which the screw point pin has a small diameter that can float and is self-centering. The pin has two support points or flats. The screw point and pin are used as a check valve in front of the piston screw of an injection molding machine for plastic materials. As a result of the small diameter of the pin the total output of plastified material is not diminished and there are no head losses. The screw point can be adapted to any models of injection molding machine, and its technical advantages give it high performance both in the field of what are known as “technical” molded parts and in the field of high-speed packaging.