Supporting tube GRP/StSt with internal sealing end and EB spring element for the HVI long Conductor to be used for the installation of a separated (insulated) air-termination system with air-termination rod. For keeping the separation distance to electrically conductive parts according to IEC/EN 62305-3. Tube D50 mm made of glass-fibre reinforced plastic (GRP), UV-stabilised, light grey colour, material factor km = 0.7. One-piece, combined with air-termination rod (D22/16/10 mm, length 2500 mm) made of StSt.