The best value in the AFR gauge market! A wideband UEGO sensor controller accurately monitors your motor's Air/Fuel Ratio (AFR) in real time to warn the user of a lean(or rich)fuel mixture, which could lead to engine damage(or catalytic damage). AEM has designed its wideband UEGO controller and gauge display into one great looking unit. AEM's UEGO Controller has unrivaled AFR accuracy and an easy-to-read digital interface. AEM??s Gauge-Type Wideband UEGO Controller features: Digital red LED display and sweeping LED ??needle?? that changes colors as AFR changes from rich to lean, green showing optimum AFR 52mm (2-1/16??) gauge housing is industry standard and fits in virtually all gauge pods, or can be remotely mounted Comes with different color bezels and faces so you can pick which color combo you like. Black/White/Silver Comes with all hardware and connectors, and includes a weld-in bung for your exhaust piping.