The conical hat is worn by all socio-economic classes and is with the ao dai unique to Vietnam. It is used to protect against the hot tropical sun or the drenching monsoon rain. It is worn by women and some men (farmers, fishermen). Having being carved on the Ngoc Lu bronze drums, it could have existed for the last 2,000 to 3,000 years.
Although there are many types of non la depending on their use, their shape remains the same. The non la is simple, light, and usually hand-made of latania (palm) leaves. A decorative non la costs more than the simple one worn by housewives.
The famous Non La Bai Tho of Hue is a hat with inscribed verses of poetry, proverb or design which can be seen as the hat is held up to the light.