This E300 HUD only compatible with universal OBD II and EOBD interface, but incompatible with OBD I or JOBD. Actually, OBD II and EOBD first applied to European and North American manufactured automobiles after 2004, and for Asian manufactured cars, they have even appeared later, since 2007. Besides, some cars, like Hummer and Savana, have special interface, may not compatible with this product, and we suggest A1 or Q7. Note: If you find out that HUD displays only voltage for 30 seconds and then turn off automatically, this is because the interface isnt OBD II or EOBD. Thus, we suggest checking twice whether your interface is OBD2/EOBD or not before purchasing. For old cars, you should set your start voltage at 12.8V, for your battery is too old to provide 13.2V voltage. The speed this HUD displays is 5km faster than actual speed by factory default. You can fine tune or adjust it to your personal preference. Features: -Auto-matching automobile models of OBD II or EOBD(European On-Board Diagnostics), plug and play. -Detect all the important driving information via the OBD II system. -2D visual effect. -5.5 inch very large high definition display. -Multi-color display offers more abundant and easy-to-read frames. -Adopted nano-technology eliminates unwanted reflection to present more definition frames. -Display rich contents: speed, engine rpm, water temperature, voltage, instant fuel consumption, average fuel consumption, local time, traveling hour, mileage, driver fatigue reminding, low voltage alarm, high water temperature alarm, over-speeding alarm, engine failure alarm, trouble code elimination, km/mile free shifting. -Automatically turn on and off in accordance with the car, which will effectively protect the car battery. Except, remained manual switch is for your better control of this HUD. -Automatic and manual brightness adjustment: non glaring light while driving. Specification: Type: Head up display E300 Display type: Digital Car Model: With On-Board Diagnostic OBDII interface Product Size: (5.12 x 2.96 x 0.59)" / (13 x 7.5 x 1.5)cm (L x W x H) Projection Size: 5.5 inch Environment: ~40c+80c atmospheric pressure 86-106kpa Alarm sound level: >>=30db Working voltage: DC9-16V Working current: 400mA Sleeping current: 15mA Speed range: 0-400KM Package Include: 1x OBD II Head up display 1x OBD Cable 1x Non-slip Mat 1x Reflecting Film 1× User Manual