This is a tablet mount for an XBox One Controller. Specifically it was designed for an 8" NuVision TM800W610L Tablet but It might work with other 8" tablets as well. I also have a version that will work with an iPhone 6+ with a slim case for use with SmartGlass .
The XBox controller has the audio port open. There is also a hole to keep the grip from pressing the sync button, which I found to be a problem with another grip on this site.
The idea was that this $80 Windows 10 tablet (though it could be found much cheaper), when paired with a USB Wireless AC adapter and a Bluetooth XBox One S controller becomes a perfect device for Steam and XBox One streaming. Plus it can do some lightweight gaming and emulators on its own. It isn't quite a Nintendo Switch, but it isn't too shabby for ~$150.
I recommend a 1 1/4" #8 screw to assemble the two pieces.
I also recommend putting electrical tape over where the grip touches the controller and tablet to prevent scratching.