A single stage liquid ring pump suitable to achieve deep vacuum (down to 33 mbar abs). This model is characterized by being bare shaft pumps, so that the device is secured by a flexible coupling that makes the pump shaft integral with the motor shaft. The reference operating speed is the 4 pole motor speed. The pumps are characterized by the presence of two big manifolds, that allow distributing/collecting the gas to/from the end casing located on both impeller ends. The shaft seal is made by means of a simple acting mechanical seal, one on each pump end.