The Monoprice 363 coupler makes it possible to connect a USB B cable to a USB A port for a low cost. It's compatible with USB 2.0 and backwards compatible with USB 1.0 and 1.1. For example, some desktops have integrated USB B connectors. Instead, you can plug in this adapter to turn it into a useful USB connection compatible with most of your devices rather than an almost useless USB B. This is useful if you need a USB A M/M cable and only have a USB A to B M/M cable handy. Note that the maximum reliable length for standard USB cables is about 15 feet; beyond that you'll need active USB extender cables.