Auto Meter 4328 Ultra-Lite Mechanical Nitrous Pressure 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 Gauge kit includes, bulb and socket assembly, red and green bulb covers, mounting hardware, and detailed instructions for installation Gauge threaded for -4AN, allowing an easy installation into the nitrous system