Awesome project! Did you create an actual HUD (projector) or just use the reflection off the windshield at night? (I emailed you as well)
In the video they say that they used 40/60 beamsplitter glass. It reflects the tablet directly.
He was asking the commenter a question about his project not Navdy.
The Navdy video has no explanation of what they use. The commenter linked to a YouTube video about his project, in which they say they used 60/40 beam splitter glass.