Abstract: A gauging installation for a tank with a long narrow nozzle providing access to an interior of the tank. The gauging system includes a GWR level gauge with a probe, and a first rigid extension member providing an interior probe mounting position at the end of the nozzle. The probe is configured to guide an electromagnetic transmit signal from a transceiver towards the product inside the tank, and to return the electromagnetic echo signal resulting from a reflection of the electromagnetic transmit signal by a surface of the product. A microwave transmission line connects the transceiver and the probe. With this design the beginning of the probe of the GWR level gauge will be located at the lower end of the nozzle, i.e. at the upper interior of the tank.