A guided wave radar level gauge for determining a filling level of a product contained in a tank, which level gauge comprises: a transceiver for transmitting electromagnetic transmission signals and receiving reflected electromagnetic signals reflected at a surface of said product; processing circuitry connected to said transceiver and configured to determine said filling level based on said received reflected electromagnetic signals; a single conductor probe configured to guide said electromagnetic transmission signals towards said surface and to guide said reflected electromagnetic signals back to said transceiver, said probe comprising at least two elongate probe sections (202, 206), each probe section being electrically conductive and having a circular cross section; wherein a connector (204, 230) permanently attached to and extending from a first end portion of each probe section comprises: an abutment portion (212, 232) having a diameter smaller than a diameter of said probe section; an intermediate portion, arranged between said probe sectior and said abutment portion (212, 232), said intermediate portion having a diameter smaller than said abutment portion (212, 232); and an outside threaded portion; wherein a second end portion of said probe section comprises: a sleeve permanently attached to said probe section and comprising a receiving portion being inside threaded and configured to receive said outside threaded portion of said connector (204, 230); a passage through a sidewall of said sleeve, said passage being located off-center in relation to a longitudinal central axis of said probe section, such that said passage is located radially outside of said intermediate portion and radially inside of said abutment portion (212, 232) when a connector (204, 230) of a first probe section is fitted in a sleeve of a second probe section; and wherein said probe further comprises a locking pin (302, 304, 306, 308) configured to be arranged in said passage such that said first probe section is locked to said second probe section by limiting movement of said abutment portion (212, 232) in a longitudinal direction. a transceiver for transmitting electromagnetic transmission signals and receiving reflected electromagnetic signals reflected at a surface of said product; processing circuitry connected to said transceiver and configured to determine said filling level based on said received reflected electromagnetic signals; a single conductor probe configured to guide said electromagnetic transmission signals towards said surface and to guide said reflected electromagnetic signals back to said transceiver, said probe comprising at least two elongate probe sections (202, 206), each probe section being electrically conductive and having a circular cross section; wherein a connector (204, 230) permanently attached to and extending from a first end portion of each probe section comprises: an abutment portion (212, 232) having a diameter smaller than a diameter of said probe section; an intermediate portion, arranged between said probe sectior and said abutment portion (212, 232), said intermediate portion having a diameter smaller than said abutment portion (212, 232); and an outside threaded portion; wherein a second end portion of said probe section comprises: a sleeve permanently attached to said probe section and comprising a receiving portion being inside threaded and configured to receive said outside threaded portion of said connector (204, 230); a passage through a sidewall of said sleeve, said passage being located off-center in relation to a longitudinal central axis of said probe section, such that said passage is located radially outside of said intermediate portion and radially inside of said abutment portion (212, 232) when a connector (204, 230) of a first probe section is fitted in a sleeve of a second probe section; and wherein said probe further comprises a locking pin (302, 304, 306, 308) configured to be arranged in said passage such that said first probe section is locked to said second probe section by limiting movement of said abutment portion (212, 232) in a longitudinal direction. an abutment portion (212, 232) having a diameter smaller than a diameter of said probe section; an intermediate portion, arranged between said probe sectior and said abutment portion (212, 232), said intermediate portion having a diameter smaller than said abutment portion (212, 232); and an outside threaded portion; wherein a second end portion of said probe section comprises: a sleeve permanently attached to said probe section and comprising a receiving portion being inside threaded and configured to receive said outside threaded portion of said connector (204, 230); a passage through a sidewall of said sleeve, said passage being located off-center in relation to a longitudinal central axis of said probe section, such that said passage is located radially outside of said intermediate portion and radially inside of said abutment portion (212, 232) when a connector (204, 230) of a first probe section is fitted in a sleeve of a second probe section; and wherein said probe further comprises a locking pin (302, 304, 306, 308) configured to be arranged in said passage such that said first probe section is locked to said second probe section by limiting movement of said abutment portion (212, 232) in a longitudinal direction.