The Mackwell Advanze-2 ST681 is an emergency inverter for use with T5,High Output and Long single turn high efficiency 80w tubes. It has a 3 hour duration and should be used with a 6 cell battery pack. These inverters have several features including: Switch Mode Power Supply for thermal overload protection and Cathode heating ensures safe and reliable starting of T5 lamps in a variety of conditions and uses.