Got around to looking at the internals of the X3 Pro, as I suspected there is a SIM reader on the motherboard and a spare M.2 slot for a 4G modem. The build quality is good, nicely laid out. Good to see Teclast used some copper in there on the heatsink and not aluminium. I would have thought they would have used a thermal pad on top of the heatsink to transfer heat to the rear alloy casing like Cube. The written review will be online soon!