Review on Universal Car HUD Head Up Display - ACECAR Digital GPS Speedometer With MPH Speed, Compass, Fatigue Driving Reminder, Distance, Altitude, Overspeed Alarm And HD Display, Suitable For All Vehicles by Kendrick Dooley

After driving over 300 miles using the device, I have some comments. The ACECAR digital speedometer is an interesting addition to your vehicle and, I must admit, a worthwhile one. The display has important information, and the unit can be "adjusted” to the vehicle’s true speed using another reliable method. I used an iPhone app that is supposed to be accurate and found it to be 2-3 mph high, so I adjusted and all was good after that.It is always a good idea to verify the accuracy of your speedometer after you replace the original tires but how is it done? I have used phone apps that provide traffic, etc. information and that displays your "actual” speed so far. The ACECAR Digital GPS Speedometer is an additional method to ensure you are maintaining safe speeds consistent with traffic signs. The additional information provided is good but I was only interested in the speedometer and altitude functions. We live and drive in the northern Rockies and live at 5,500 feet and routinely drive to much higher altitudes. I am always fumbling with the iPhone compass app to see our altitude and wonder how accurate it is. Well, the altitude function is a major FAIL and disappointed me. I could not figure out what the reading meant nor was my question on Revain answered.There are several mounting options provided including a glass mount and 2-sided tape. Until I can figure a legal method to mount this, I am temporarily placing it in a large cupholder on the center console that should not alarm the constabulary.Like: The display readability in all light levels, the speed, direction, and GPS information.Dislike: The instructions are a fail. The altitude readout is a fail. The time is not worth using.