A radar level gauge system for determining a filling level of a product in a tank, said radar level gauge system comprising: a transceiver for generating, transmitting and receiving electromagnetic signals; an elongated two-conductor probe having a signal conductor connected to said transceiver, and a rigid shielding conductor spaced apart from said signal conductor by an open space, said two-conductor probe extending from an upper probe end to a lower probe end for guiding an electromagnetic transmit signal from said transceiver along said two-conductor probe towards and into said product in the tank, and for returning an electromagnetic surface echo signal resulting from reflection of said transmit signal at a surface of said product back towards said transceiver; and processing circuitry for determining said filling level based on said transmit signal and said surface echo signal, wherein said shielding conductor exhibits an open cross-section profile, in a cross-section with a plane perpendicular to said two-conductor probe, along at least a portion of said two-conductor probe; and wherein said two-conductor probe further comprises a plurality of spacer arrangements (55a-c) arranged in spacer regions (57a-c) spaced apart along said two-conductor probe, each spacer arrangement in said plurality of spacer arrangements including at least a first spacer member (59a-c) attached to said rigid shielding conductor and arranged between said signal conductor and said rigid shielding conductor for preventing contact between said signal conductor and said shielding conductor, wherein said shielding conductor surrounds said signal conductor by an enclosing arc angle (θ) around said signal conductor greater than 180° and smaller than 330° along said portion of said two-conductor probe. a transceiver for generating, transmitting and receiving electromagnetic signals; an elongated two-conductor probe having a signal conductor connected to said transceiver, and a rigid shielding conductor spaced apart from said signal conductor by an open space, said two-conductor probe extending from an upper probe end to a lower probe end for guiding an electromagnetic transmit signal from said transceiver along said two-conductor probe towards and into said product in the tank, and for returning an electromagnetic surface echo signal resulting from reflection of said transmit signal at a surface of said product back towards said transceiver; and processing circuitry for determining said filling level based on said transmit signal and said surface echo signal, wherein said shielding conductor exhibits an open cross-section profile, in a cross-section with a plane perpendicular to said two-conductor probe, along at least a portion of said two-conductor probe; and wherein said two-conductor probe further comprises a plurality of spacer arrangements (55a-c) arranged in spacer regions (57a-c) spaced apart along said two-conductor probe, each spacer arrangement in said plurality of spacer arrangements including at least a first spacer member (59a-c) attached to said rigid shielding conductor and arranged between said signal conductor and said rigid shielding conductor for preventing contact between said signal conductor and said shielding conductor, wherein said shielding conductor surrounds said signal conductor by an enclosing arc angle (θ) around said signal conductor greater than 180° and smaller than 330° along said portion of said two-conductor probe.