Black belts are all those who have achieved the Dan level. However, black belts are all students who have reached the minimum level of 1st Dan and have no interest in becoming instructors, therefore, they remain simple students and have no teaching qualification.
They wear the same white/red student Gi. Yet, as well as instructors, on official events, they will have to wear the winter uniform with its black belts badge with the flag of their country on the chest. While, in the Summer, they will have to wear the Summer uniform, which is exactly the same as for Instructors (see uniform links).