Ao tac is a variant of the ao dai, but it has loose and large sleeves. This is considered the national costume of the Nguyen Dynasty, because ao tac can be worn by any class in society, from the royal, the officials, to the middle and lower class, and can be worn by both men and women.
Ao tac was worn in important ceremonies and occasions such as a wedding, funeral, Tet, and worship events. This action is to hide both hands and show the humbleness, respect, and elegance in crucial events.
