[3 Ways]Fix SD Memory Card Wont Mount Unmounted on Phone or Windows ...
The Sony A7rIII has some new internal hardware that allows for faster memory card performance, a larger buffer, as well as UHS-II memory cards.
Sony A7riii Memory Card
The Sony A7rIII has two memory card slots but only one takes UHS-II cards. So you can either buy both UHS-II cards and not worry about mix and matching, or save yourself some money and buy a UHS-I card for the UHS-I slot.
Memory cards for Sony A7C | JuzaPhoto
Memory cards for Sony A7C...