The AEM E85 Wideband O2 UEGO Gauge is a must for anyone that has started looking for more power from their engine running E85 (Ethanol). Air/Fuel ratio is one of the most important things to know when tuning your engine. Running rich can cause you to lose power, running too lean can result in serious engine damage. The 320 degrees of resolution makes it easy to see when there's even a half a point change in ratio, giving you time to shut things down before damage occurs. The lightning fast needle movement is a result of a precision high speed electronic stepper motor making it one of the fastest and most accurate gauges available. A Bosch 4.2LSU sensor gives the gauge its accuracy, and is the same base sensor used in many OEM applications today. The backlighting is user adjustable to 7 colors, allowing users to easily match the Air/Ratio gauge to most factory gauge clusters. Each gauge comes with interchangeable black & silver bezels and black and white gauge faceplates for multiple color combinations.