The clothing in which a woman appears before
non-mahram men must meet eight conditions:
1- It should cover the entire body, including the face and hands. The evidence for that has been discussed in the answer to question no. 11774.
2- It must be wide and loose, not showing the size of her limbs or the shape of her body.
3- It should not be thin, showing the colour of her skin.
4- It should not be an adornment in and of itself, such as clothing decorated with embroidery.
5- It should not be perfumed.
6- It should not resemble the clothing of men.
7- It should not resemble the dress of kaafir women.
8- It should not be a dress of fame and vanity.
See Adaab al-Zafaaf by Shaykh al-Albaani (may Allaah have mercy on him), p. 177; Hijaab al-Mar'ah al-Muslimah, p. 16-111; 'Awdat al-Hijaab, 3/145-163.
Why do women cover their hair?