High Quality Content by WIKIPEDIA articles! Obi is a sash for traditional Japanese dress, keikogi worn for Japanese martial arts, and a part of kimono outfits.The obi for men's kimono is rather narrow, 10 centimetres (3.9 in) wide at most, but a woman's formal obi can be 30 centimetres (12 in) wide and more than 4 metres (13 ft) long. Nowadays, a woman's wide and decorative obi does not keep the kimono closed: this is done by different undersashes and ribbons worn underneath the obi. The obi itself also requires the use of stiffeners and ribbons.