6. Contestants must keep their hair clean and cut to a length that does not obstruct smooth bout conduct. Hachimaki (headband) will not be allowed. Should the Referee consider any contestant's hair too long and/or unclean, he may disbar the contestant from the bout. Hair slides are prohibited, as are metal hairgrips. Ribbons, beads and other decorations are prohibited. A discreet rubber band or pony tail retainer is permitted. Female competitors may use religiously mandated head-wear of a type approved by the WKF.