Background Trimming (Oval) Description
A black oval shaped embroidered item edged with a 1/8 inch (.32 cm) white outer border and a 1/4 inch (.64 cm) inner border with two black hash marks, one to left and one to right, 1 3/8 inches (3.49 cm) in height by 2 1/4 inches (5.72 cm) in width overall. 

History
The background trimming was approved on 23 November 2005.  It was amended to change the description/design on 5 January 2006.

Source: The US Army Institute of Heraldry