Traditional incandescent lighting illuminates around the perimeter of the dial. Autometers Race Proven Mechanical Instruments Provide Trusted Accuracy While Being Simple To Install. No electrical system required for gauge operation - compatible with every street or race vehicle. Mechanical movements provide accuracy and durability even in the harshest environments. Gauge kit includes 1/2" NPT adapter bulb and socket assembly red and green bulb covers mounting hardware and detailed instructions for installation