The mount is made of metal, and it doesn’t have any dust protective rubber ring.
I suppose a simple protective rubber ring won’t increase too much the overall manufacturing costs by adding to the lens, but of course I’m not familiar with this, so I’m just making a simple guess.
Still, the absence of a protective ring is something that I always note on nearly all the latest Tokina lenses, as I feel it is a very small detail that makes a great difference.
In the mount there are of course electronic contacts to provide full communication with the camera body, so all camera features like Autofocus, Electronic Aperture Change, EXIF Data, In-Camera Corrections and In-Body Image Stabilization* (IBIS) will work perfectly
(*in case the selected camera model has this feature)
Lastly, in the top of the mount, opposite to the electronic contacts, we find a micro USB port, that can be used for future firmware, something that ensures that the lens will work ideal with upcoming new camera models in the future.