Abstract: An illuminable unit includes a light tube having a spiral-shaped light body containing a mercury source therein and two end portions downwardly extended from the light body, a cathode terminal supported at the end portion of said light tube. A conductor enclosure, which has a length approximately equal to a length of the end portion of the light tube, has an upper head portion sealedly mounted within the respective end portion of the light tube in a concealed manner so as to substantially reduce an overall height of the illuminable unit. A conductor wire is electrically extended from the cathode terminal through the conductor enclosure to an exterior of the light tube for electrifying said mercury source while electrical connection.