The ViscoTec preeflow® eco PEN600 has been developed and tested for precise dispensing of media with low to high viscosity at highest repeatability. The preeflow dispensers are rotating positive displacement pumps. The conveying elements consist of a rotating part, the "rotor", and a stationary part, the "stator". The rotor, which is designed as a kind of round thread, moves rotationally in the stator, which has one more thread and twice the pitch length of the rotor. This leaves conveying spaces between the stator and the rotor, which rotates in it and also moves radially, and moves forward continuously. The flex shaft driving the rotor compensates for the eccentric movement of the rotor and is completely maintenance-free. The sealing effect of the dispenser's conveying elements is viscosity and pressure dependent. Since the conveying direction is reversible, the medium can be retracted for a clean thread break.