QUALITY ASSURANCE -- CE FCC ROHS certification, excellent quality. High performance chip, which has strong performance and compatibility, ensures the high-speed operation of dual system, dual running memory and dual core processor. If you have any questions, please feel free to contact us., we will get back to you as soon as possible to help you solve the problem. COMPATIBILITY ISSUE --- OBD II is only applicable to vehicles manufactured after 2008. GPS mode is applicable to all vehicles( If your car is not compatible with OBD mode, please select GPS mode.) Dual system, no return and exchange. OBD ll is not compatible with electric vehicle, diesel vehicle, pickup truck, RV and computer modified vehicle, so GPS mode is recommended. MULTI FUNCTION DISPLAY--- In the OBD mode, it can display: speed, water temperature, voltage, driving distance, with the functions of speed alarm, water temperature alarm, voltage alarm, etc.GPS mode can display: speed, voltage, driving distance, with speed alarm , voltage alarm function. HUD can automatically adjust the brightness according to the environment. Speed unit: km / h or MPH. The unit of water temperature is degrees centigrade and degrees Fahrenheit. The unit is adjustable. INSTALLATION --- The installation is simple and convenient, plug and play, and it won't damage your car at all. HUD --- Is the abbreviation of head up display. It displays driving data on the front windshield, such as speed, water temperature, voltage, etc., which is derived from the high technology of fighter. HUD can not change the way the driver looks at the dashboard while driving, avoiding the danger of the driver looking down at the dashboard.