an electrofusion coupling for coupling a first device to a second device , includes a first part having an outer end for coupling to the first device , and an inner end formed with a surface of a curved configuration ; and a second part having an end engaging the inner end of the first part and formed with a surface of a complementary curved configuration as the first part . the curved configurations of the two parts is such that the second part may be pivoted to locate its longitudinal axis at different angles with respect to the longitudinal axis of the first part . at least one of the parts is of a thermoplastic material and includes an electrical heater coil embedded along its curved surface for fixing by electrofusion the angular position of the second part with respect to the first part .