The invention provides an improvement in the means for supporting a container of effusive material located on the terminal end of an antenna-type positioning member for use in a cathode ray tube. The supporting structure is comprised of a rotatable member accommodated on axle means affixed to the positioning member at a region rearward from the forward edge of the material container. An augmentive fender-like protective component is associated with the rotatable member to shield that member from effusive material and to prevent any accumulated electric charge thereon from interfering with the scanning of the electron beam in the tube.