Geometric flush mount vent covers
These flush mount vent covers are easiest to install when building new construction because then they can easily be built into the wall. Retrofitting can be difficult. Take a look at the pdf install guide and you'll see what the story is. Still, when you get done you have a great clean looking installation.
The grilles are held in place by very strong magnets that take a lot of pulling to dislodge. Feel free to install in a ceiling. They certainly will not be falling on your head with the high strength magnets.