Final answer:
The authorized flash for wear on the black beret in the U.S. Army is the distinctive unit insignia flash of the soldier's assigned unit, with each unit having its own unique flash. Soldiers in units without a unique flash use the default Army flash.
Step-by-step explanation:
The only authorized flash for wear on the black beret in the United States Army is the distinctive unit insignia flash representing the unit to which the soldier is currently assigned. The beret flash is a unique insignia that identifies a soldier's unit and is worn on the left front of the beret. The flash is oval shaped and contains the colors and design representative of the soldier's particular unit, with each unit having its own unique flash. Soldiers assigned to units without a unique flash wear the default Army flash, which is a teal blue oval with 13 white stars.