Auto Meter 4331 Ultra-Lite Mechanical Water Temperature Gauge Traditional incandescent lighting illuminates around the perimeter of the dial Auto Meters 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