The invention concerns the field of needless syringe for injecting liquid active principle for therapeutic purposes. Accordingly, undercut, overhang, and mouse bites which may arise in an etching process, are prevented, and TFT array panels that have signal lines having low resistivity and good contact characteristics are provided. 5 inch H2O pressure drop and an original filtration efficiency greater than 99. A putter face and a chipper face are provided, respectively, on opposite side surfaces of the head. The device can for instance be used for reversing the flow in an extracorporeal blood circuit.