Background Trimming (Oval) Description
A white oval-shaped embroidered item 1 3/8 inches (3.49 cm) in height by 2 1/4 inches (5.72 cm) in width overall surmounted by an inner oval approximately 1 1/2 inches (3.81 cm) in width and 3/4 inch (1.91 cm) in height overall and divided vertically into three equal stripes of red, white and blue all within a 1/8 inch (.32 cm) white edging, containing one blue horizontal stripe approximately 3/32 inch (.24 cm) in width added to both sides of the white background at horizontal axis.

History
All the background trimmings were approved on 23 May 1968.

Source: The US Army Institute of Heraldry