Abstract: An inflatable pipe plug in which a series of reinforcing strips of rubber tire cord having unidirectional threads are sandwiched between inner and outer molded members of rubber. The strips include pairs crossing each other with their threads at angles to each other. One underneath sleeve-like strip is longer than the two molded rubber members and is folded back over other strips. A metal head has a tubular portion fitting into the interior of the inner rubber member and is vulcanized to it and also to an inner sleeve of rubber which is somewhat longer than the aluminum head and extends beyond it and is bonded also to the inner rubber member. The structure enables the plug to withstand stress when compressed air is supplied to it through a cap that is bolted to the aluminum head.