Hopefully you are not pulling our collective legs................ FYI: Tube Shield: A metallic enclosure placed over a vacuum tube to prevent external fields from interfering with the function of the tube. Further, in some cases it is used to dissipate extreme heat, generated within the tube and hopefully make it run cooler, thereby lengthening its useful life.... i.e. IERC or EBY shields. 73/jim/W0JJL