An item consisting of one or more definite lengths of straight or formed, flexible or rigid, prefabricated hollow tubing of conductive material. the tubing has a predetermined cross section and is designed to guide or conduct high frequency electromagnetic energy through its interior. one or more ends are terminated. may include common mounting of a switch, wave guide, a dummy load, electrical and other components such as waveguide section, cable terminal chamber and the like. excludes coupler, rotary, radio frequency; coupler, directional; adapter, waveguide; and tuner, waveguide.