I picked this up from TEK Nemesis years ago, the original design being done by Ryzee119 (Ryan Wendland). This awesome little box connects to each port of your Original Xbox using the included cables and allows using the included Xbox 360 dongle to wirelessly connect up to 4 wireless Xbox 360 controllers. You can also use it to directly connect a 8bitdo wireless Bluetooth adapter to support everything it can support, emulate the Steel Battalion controller with a 360 Chat Pad and more!

A bit of cool retro-scene history that can be super useful. My xbox mods hoarding could be your gain!

More info on the adapter here: 

https://github.com/TEK-Nemesis/ogx360