Emergi-Lite/Lumacell ET/LT Power Free exit signs. Illumination provided by borosilicate glass tubes, internally coated with zinc sulphide phosphor and filled with tritium gas. Decorative, slim-line heavy-duty ABS housing and rugged, impact-resistant polycarbonate face. Spark-free construction. universal direction capability, comes complete with universal mounting hardware. Stands up to extreme temperatures in outdoor or indoor applications. Life expectancy of 10 or 20-year (EXIT).