The Edelbrock part # 6593 Narrow Band LED Air-Fuel Ratio Monitor was designed for use with all aftermarket carburetor and EFI kits. The kit comes complete with an LED light display, oxygen sensor, sensor bung and wire harness. Installation Notes: '- All electronics, circuits and LED display are contained in a plastic enclosure approximately 1.5" H x 3.0" W x 2.0" D - The display consists of 7 LEDs calibrated to integer units of Air/Fuel ratio from 12 to 15 AFR. - The leaner light (1) is red, the center lights (4) straddling "stoich" are green, and the richer lights (2) are yellow - Racing fuel or fuel that has a high lead content or use with alcohol will cause premature failure of the oxygen sensor - You can use the A/F Monitor to properly adjust all of your carburetion circuits including idle, cruise, and power - To prevent catastrophic failure of unit, avoid routing wires near spark plug wires. - DO NOT USE VEHICLE SHEET METAL AS A SYSTEM GROUND. - Use care in routing wires near or around hot exhaust components. Shorting the O2 sensor signal to ground may permanently damage the sensor - Do not look at the monitor any longer than necessary during Wide Open Throttle operation, especially in high performance vehicles. Have someone ride with you and observe the monitor while you watch the road.