in a plastic pipe joining system a plastic sleeve is provided to extend on both sides beyond the region of contact or closest approach to one another of pipes to be joined with the sleeve being fused to both pipes , the sleeve heated to curie temperature of high mu material excited by an externally generated high frequency magnetic field . the heater may be embedded in the sleeve and the sleeve may also be employed with end caps that extended over the sleeve , the end caps and sleeve being fused to one another and the pipes by heaters carried by the end caps or the sleeve . an external heater may also be employed which in conjuction with shaped end members provides the sleeve with beveled or tapered edges to enhance the ability of the sleeve to withstand cracking .