Wireless Joint

That device is still "compatible" with ATT / Cricket Wireless.

Does anyone know what modem is in it?

I think it's a Snapdragon X16?
https://www.qualcomm.com/snapdragon/mod ... 4g-lte-x16

Anyone know if you can only use these embedded in the device?

Qualcomm MDM9250.

Source: Defcon presentation by G. Richter: Reverse Engineering 4G Hotspot for Fun, Bugs and Net Financial Loss
https://media.defcon.org/DEF%20CON%2027 ... l-Loss.pdf