Utilizing the latest Bosch wideband 5 wire heated O2 sensor, this Prosport gauge has the widest range 10.0:1 to 20.0:1 AFR readings on the planet. An Amber LCD readout in the center of the gauge and a bar-graph syle LED's around the outside of the gauge that changes from green (Rich) to Yellow (Optimal) to Red (Lean) for immediate reference to AFR.