What is HUD?It displays driving data on the front windshield such as speed,RPM,water temperature,voltage single mileage,compass,digital clock,etc.3.5-inch HD display,zero double images, clearly reflection on the windshield,it is pretty clear in thesunny day,rainy day. It avoids the danger of the driver looking down at the dashboard, which ensures the driver's safety and helps the driver stay in top condition. Button FunctionFunction:speed,engine RPM,water temperature,voltage,km/mph switch,power test,single mileage measurement,Water temperature icon,clean fault code,fuel consumption,compass,time.You can toggle the function you want to display with the button.Thereare two USB ports,you can choose one according to your needs(Note:only one interface needs to be connected.Plugging in two ports at the same time could burn out your car.) Simple and Practical FunctionWhen your vehicle breaks down, the clear fault code function can help your car clear fault codes without you having to spend extra money to go to the repair store. It also has 5 kinds of abnormal alarm functions, over speed,engine RPM, water temperature, voltage, fatigue driving and other alarm functions to make driving safer and easier. Plug & play Easy to InstallThis unit has equipped with 2 cables:OBD2 and USB cable.We do not need to damage your car but just plug them in,then you can use it and modify your car.OBD2 mode is only applicable to most vehicles manufactured after 2008(ifyou want to use OBD2 mode,please check whether your vehicle has OBD2 protocol or contact us for confirmation before purchase).The GPS mode is perfect for all vehicles.(if your car is not OBD compatible,use GPS mode.)Dual System,Change free. The chip with powerful performance and compatibility to make sure dual system, dual-run memory and dual-core processor high-speed operat.