Refreshable braille displays provide braille via a set of little rods, representing braille code. As the application focus is moved, or a document is read, the braille display changes. These displays provide computer access for people who are deaf-blind, as well as blind people who prefer this output to speech (or with speech). The length of the displays vary with models offering 20, 40 or 80 cells. Screen reading software is required to work with the hardware.