a cylindrical tubular body where flanges are respectively formed on an outer peripheral surface of a first end portion of the cylindrical tubular body and on an outer peripheral surface of a second end portion of the cylindrical tubular body on a side opposite to the first end portion in an axial direction of a tubular body, the flanges being integrally formed on the tubular body in a protruding manner toward an outer side in a radial direction;

a first connection tubular body disposed on a first end portion side of the cylindrical tubular body, and having male threads on an outer peripheral surface of the first connection tubular body;

a second connection tubular body disposed on a second end portion side of the cylindrical tubular body, and having male threads on an outer peripheral surface of the second connection tubular body;

a tube joint which connects the cylindrical tubular body and the first connection tubular body to each other; and

a tube joint which connects the cylindrical tubular body and the second connection tubular body to each other, wherein

both the tube joint and the tube joint each include:

a cylindrical pawl equipped nut where female threads which are threadedly engageable with the male threads formed on the first connection tubular body or the male threads formed on the second connection tubular body are formed on an inner peripheral surface of the cylindrical pawl equipped nut, a plurality of pawl portions which are engageable with either of the flanges of the cylindrical tubular body are formed in the cylindrical pawl equipped nut in a circumferential direction and in a protruding manner toward an inside in a radial direction, the plurality of pawl portions are configured to get over the either of the flanges of the cylindrical tubular body and to engage with the either of the flanges, and the female threads are configured to threadedly engage with the male threads of the first connection tubular body or the male threads of the second connection tubular body so as to bring about a fastening state of the cylindrical pawl equipped nut thus enabling connection between the first connection tubular body and the cylindrical tubular body or connection between the second connection tubular body and the cylindrical tubular body; and

a retaining ring being annularly mountable on an outer peripheral surface of the pawl equipped nut, the retaining ring being capable of retaining engagement of the plurality of pawl portions with the either of the flanges of the cylindrical tubular body, and

the plurality of pawl portions of the pawl quipped nut are each formed on each of distal end portions of a plurality of protruding lugs formed on the pawl equipped nut in a protruding manner in an axial direction at a predetermined interval in a circumferential direction, and the plurality of protruding lugs have elasticity in a radial direction, and

the retaining ring is annularly mounted on the plurality of protruding lugs, and the retaining ring is configured to impart a pressing force to the plurality of pawl portions in a radial direction in a state where the retaining ring is annularly mounted on the plurality of protruding lugs.