all members of the order of st. john are also required to wear specific robes for formal occasions of the society, including a mantle, sopra vest, and hat. the mantles of the sovereign head and grand prior are all of black silk velvet and lined with white silk, the former's differentiated by an additional train. bailiffs and dames grand cross and, prior to 1926, knights of justice formerly wore black silk robes with a lining of the same material and colour; these members now wear the same mantle as commanders, officers, and esquires, which are made of black merino wool faced with black silk. the only other unique mantles are those of the medical officer of the st. john ophthalmic hospital, which bears a special pattern, and of chaplains, which is a black silk robe with full sleeves. each cloak also bears on its left side a rendition of the order's star in white silk: the sovereign head, grand prior, and those in the first two grades of the order all have a diameter emblem; the sovereign's and grand prior's are of white silk with gold adornments, the former's also surmounted by a st. edward's crown, while those for bailiffs and dames grand cross, knights and dames of justice, and knights and dames of grace are rendered in white linen, the first two groups having embellishments in gold silk, the latter in white silk. similarly, the star for commanders and officers is of white linen with white silk ornamentation, though they are only and in diameter, respectively. the secretaries of the order, the priories, and the commanderies also wear the badge superimposed upon two goose quill pens embroidered saltire-wise in white silk.