In the United States, heraldry is not governed by any official authority; but the United States Army, which makes extensive use of heraldry, does have its own authority, the United States Army Institute of Heraldry. The armorial designs of the Institute of Heraldry include a number of novel tinctures, including "buff" (employed variously as either a metal or a colour), and "horizon blue". "Silver gray" has appeared in the heraldry of both the Army and the Air Force. "Bronze" appears as a colour in the arms of the Special Troops Battalion of the 2nd Brigade, 1st Cavalry Division. There seems to be some confusion about the colour "crimson", as in some cases it is treated as a separate tincture, while in others it is used to specify the shade of gules to be employed by the artist. Differing from most heraldic practice, the Institute of Heraldry often specifies the exact shades to be used in depicting various arms.