This is a mount for Viso visual altimeter. There are two versions: one for velcro strap and one for elastic (images show a mixed of them: velcro version with elastic strap!).
It was printed in TPU material (elastic like rubber).
The idea of this design is to have a better view of the screen.
I don't know if it fits the newer Viso's (II, II+) as I don't have any of them.