When selecting TFT displays, you are usually stuck with standard dimensions. The aspect ratio, called "Aspect Ratio", describes the (visible) width in relation to the height. In the past, it was mainly 4:3 or 5:4, but today's industrial displays use 16:9. For some applications, these aspect ratios do not fit because the installation space is insufficient, an older display in a different technology (e.g. STN LCD, seven-segment LED) has to be replaced, or the content requires a different format (e.g. signposting, space reservation).
Displays with unusual sides can be produced either from the cut of a larger display or as a development in a special format. While displays with larger diagonal are usually made by cutting, smaller displays are made with square sides or with circular display area. Square or circular displays often use interfaces provided by ARM processors, namely processor buses of different widths, SPI or MIPI. In their optical parameters, they are quite comparable with large displays; high brightness is combined with current IPS technology for best reading behavior.