Abstract: A sleeve connector for connecting the ends of two tubes together, in particular socket tubes, comprises a socket formed with or connected to one of the tubes. The socket has an inner annular recess which is bounded by a conical surface which tapers radially inwardly toward an end of the socket. A retaining collar is secured around the spigot end of another tube to be connected to the first mentioned tube. At least one locking member is disposed around the spigot and is positioned in the annular recess so that it can bear against the conical surface. The locking member has an inner cylindrical contact surface which engages on the spigot and an outer contact surface which has a sectional toroidal shape wherein all normals to the toroidal shape pass through the cylindrical contact surface.