This mess dress is worn in the evenings for dining. 2A is the formal evening dress for ceremonial dinners; it consists of a navy blue mess jacket with a white waistcoat (black cummerbund for female officers) with miniature medals. For officers of the rank of captain and above, a navy blue tailcoat (known as an 'undress tailcoat') may optionally be worn in lieu of the mess jacket. For officers of these ranks; in addition, gold-laced trousers (known informally as 'lightning conductors') may also be optionally worn either with the tailcoat or the mess jacket. 2B is "mess undress" for other mess functions, and is worn with either a black cummerbund or navy blue waistcoat and miniature medals. 2C, "red sea rig", is worn for informal evening wear on board ship; it consists of a white short sleeved shirt, worn with shoulder boards, without medals and with black trousers, black shoes and a black cummerbund.