In the context of shoe sizes, the letter "B" refers to the shoe width, specifically the standard or medium width for womens shoes. For mens shoes, the standard width is typically labeled as a "D" or "DM" width. The width designations such as "B" help to ensure that shoes provide the right fit for a variety of foot shapes. Shoe boxes and labels will only identify widths other than standard. Wide and narrow widths are identified on the label, underneath the tongue. The differences of width between narrow, standard, wide, and extra wide are usually only a couple of millimeters and are proportional to the size of the shoe. Most additional width will be found in the forefoot.