Ertuğrul Börk Hat - Unarmed Product Features It is Grey in Color It Has a Warming Feature It is Faux Leather Börk is known as a men's hat or headdress among Turks. It used to be made from animal skins and processed leather, and later from felt and broadcloth. Börk was used in Turkmen tribes living in Iran and Anatolia, and in the Seljuk and Ottoman armies. It is written in sources that Osman Bey wore a red broadcloth börk. In the time of Yıldırım Bayezid, it was worn by members of the army for the first time, and after this date, it became the official headdress of the Janissary corps.