The rear armrest in the center of the rear seatback can be used (no occupant in the center seat) or placed upright.

WARNING
Never put your hands and fingers around the moving parts of the seat and armrest:
Putting your hands and fingers around the moving parts of the seat and armrest is dangerous as they could get injured.
Split Folding
Head RestraintsMazda 6 Owners Manual: Changing a Flat Tire
NOTE
If the following occurs while driving, it could indicate a flat tire.
Steering becomes difficult.
The vehicle begins to vibrate excessively.
The vehicle pulls in one direction.
If you have a flat tire, drive slowly to a level spot that is well off the road
and out of the way of tr ...
Mazda 6 Owners Manual: Head Restraints
Your vehicle is equipped with head restraints on all outboard seats and the rear
center seat. The head restraints are intended to help protect you and the passengers
from neck injury.
WARNING
Always drive with the head restraints installed when seats are being used
and make sure they are pro ...