The original and most formal model of dinner jacket is the single-breasted model. The typical black tie jacket is single-breasted with one button only, with jetted (besom) pockets and is of black or midnight blue; usually of wool or a wool–mohair, or wool-polyester blend, although other materials, especially silk, are seen. Although other materials are used, the most appropriate and traditional for the dinner jacket are wool barathea or superfine herringbone. Double breasted models are less common, but considered equally appropriate. Dinner jackets were commonly ventless before World War I, but today come ventless, with side vents, or with center vents. The ventless style is considered more formal, while the centre vent is the least formal. The lapels (traditionally pointed and shawl) are usually faced with silk in either a grosgrain or a satin weave, but can also be silk barathea. A notched lapel is not always considered to be appropriate for a dinner jacket.  However, according to the Black Tie Guide, the peaked lapel and shawl collar are equally authentic and correct. The buttons should be covered in similarly coloured material to the main part of the jacket, which would ideally be either self-faced or covered with the same material as the lapels. Some higher-end single-breasted jackets, both new and vintage, tend to be fastened with a link front closure which is visually similar to a cufflink; this method of closure is still common in the United Kingdom.