Traditional incandescent lighting illuminates around the perimeter of the dial. 12 and 16 volt compatible well-suited with nearly every street car or race car electrical system. Gauge kit includes 1/8" NPT temperature sender 3/8" and 1/2" NPT adapters bulb and socket assembly red and green bulb covers mounting hardware and detailed instructions for installation. Autometers Race Proven Air-Core Electric Instruments Provide Quick And Accurate Readings While Keeping Hazardous Fluids Outside Of The Vehicle