Abstract: An electrically nonconducting hollow-profile structural part having a protective cover, preferably made of polyester threads or fibers, with a mechanically supporting glass-reinforced plastic core, especially for SF.sub.6 insulating gas technology. The hollow-profile structural part has an end that is conically shaped and connected to an attaching element with an oppositely facing conical surface by means of conically-constructed screw and/or cemented connections in such a way that the glass-fiber interfaces of the core exposed at the end surface are covered gastight by the cone superficies of the attaching element. As a result, the SF.sub.6 insulation gas products of separation which attack glass and which develop as a result of corona discharges cannot come into contact with the glass fibers.