APSX D2 Digital Wideband O2 Air Fuel Ratio Controller All-in-One 2 1/16" (52mm) Gauge (RED) APSX WIDEBAND D2 AFR CONTROLLER Gauge features a clear LED readout and sweeping color-coded LED display. The D2 gauge is ideal for all vehicles including carbureted applications and engine dynamometers. Analog output is 0-5V and can be used with data loggers or aftermarket ECUs including the MegaSquirt PNP and others. Digital output is also available for real-time monitoring via PC or display. One of the five bright LED color options (Red / Green / Orange / Blue / White)