Brand new and never used. (This is a must have for quick and easy tuning on the 2019+ CRF110 and CRF125 using the aRacer ecu ). 1. High accuracy and high-speed response 2. "Close Loop Fuel Compensation" with RC/RCMINI Plus ECU 3. No need to calibration, just plug and play 4. AF2 uses : Bosch LSU 4.9 18mm wideband oxygen sensor ( Requires an 18mm threaded BUNG on exhaust, not included) Benefits over the old AF1: 38% Faster Response 38% Smaller Size Minimum operating voltage lower to 8.5 V 80% More accuracy 25% Less power consumption AF2 Professional AFR Module - The aRacer AF2 module is an extremely accurate autotune kit that doubles as a standalone wide-band 2 when paired with the DG1 Multi-Function Gauge or aRacer ECU/App. This will allow you to monitor your air-fuel ratios from a required 18mm O2 bung on the exhaust system. (This must be added to your exhaust on the crf110 unless you purchase an exhaust with bung already on it like the rocket big bore chubby and standard chubby with bung ready to go.) i just received it in the mail yesterday and decided to go a different route of tuning!