An equilateral triangle, one point up, above a horizontal tab attached in base, the overall dimensions of triangle and tab is 4 1/16 inches (10.32 cm) in height and 3 7/8 (9.84 cm) inches in width, the triangle is divided into three sections, the upper section yellow, the dexter section blue and the sinister section red, overall a gun bendwise in front of a tank track and wheels all black surmounted by a red lightning flash bend sinisterwise. In the apex the Roman numeral "I" in black, all within a 1/8 inch (.32 cm) green border.
Yellow, blue, and red are the colors of the branches from which armored units were formed. The tank tread, gun, and lightning flash are symbolic of mobility, power, and speed. The Corp's designation is annotated by the Roman numeral I.
The shoulder sleeve insignia was approved on 22 November 1940.