HUD short for Head Up Display. It displays driving datas on the front windshield such as speed, RPM, voltage, single driving distance etc on the car front window glass, avoiding drivers unsafety because of watching the instrument while driving.2. Multi functions unit: L/100KM=Unit of Average fuel consumption for each 100KM, L/H=instantaneous fuel consumption, RPM=Engine speed, V=Voltage, °C/°F=Water temperature in different unit, KM/M=Single Driving Distance in Kilometer or Mile.3. Drivers can read the driving information instantly, and can always keep the best state on the way with HUD.Feature: HUD Size 5.8 Inch Working Voltage DC 9V~16V(DC 12V/400m - A) Alarm Sound Level ≥ 30d - B (A) Environmental Noise ≤ 60d - B (A) Relative Humidity 10% - 95% Environment Temperature -40 bplusmn; 80 b?( atmospheric pressure 86-106KPa) HUD Installation:1. Know your vehicle brand, HUD work for cars with OBDII agreement or EU OBD agreement. Open the engine hood and find the sticker below if it has words like OBDII CERTIFIED, then it can be installed.2. Find out where the 16 pin diagnostic link of the vehicle and connect it well with OBDII connecting line. - Package Included:1 X Car HUD Head Up Display 1 X English User Manual