AEM 52mm Wideband UEGO Air Fuel Ratio Sensor Controller Gauge w/ White Face Kit X-Series Wideband UEGO AFR Controller Gauge were fastest responding wideband air/fuel ratio controllers in an independent test vs. 17 competitor wideband AFR controllers. White bezel kit included. Black bezel and black dual faced faceplate, silver bezel/white gauge option included. Display Lambda values from .55 to 2.00 Factory calibrated resistor does not require free-air calibration, but technology allows for free-air calibration as sensor ages if user desires. Includes Bosch 4.9LSU wideband UEGO sensor. 52mm gauge diameter and slim 0.825 gauge depth.