The twenty-five Gs400 1979 (n) (e01 E02 E04 E17 E18 E21 E22 E24 E25 E30 E34 E39) Special Market (e21) (gs400c.en.n:~f.no.71031) (gs400en: component parts are all listed in this schematic.
Of all the components used in this assembly the Tube,inner is the most expensive.