These used to be readily available in the late 80s early 90s, Most of the manufacturers who used to make them have stopped. Guess the demand is a lot lower now that everyone is hooking up their gear to pcs. But for midi controlled rigs they can be useful to allow you to down load, upload , modify patches on all your midi controlled gear without having to unplug cables left right and centre. I reckon a singke 19" rack unit or maybe even a half rack unit would be suitable for most peoples needs