Abstract: A fluit-tight connector comprising two members with respectively concave and convex co-operating mating ends and joined together by an internally threaded sleeve retaining one of the members and tightened by being screwed onto the other member by means of a bush externally coaxial with the sleeve and comprising an inner toothing co-operating with the outer periphery of the sleeve, the bush having such a length that after screwing of the sleeve and axial sliding of the bush over the sleeve it covers and engages with its inner toothing the outer periphery of one member for locking this member as well as the sleeve against rotation.