According to its description, the Anker USB 3.0 card reader can handle both a MicroSD and a standard SD card at once:
Simultaneously read and write on two cards to save yourself the effort of constant unplugging and re-plugging.
Which looks like this:
After you get used to inserting the SD card downside-up, it fits perfectly. The Kapton tape on the MicroSD card eases extraction from the still finger-dent-less M20 camera mount on the back of my Tour Easy ‘bent.
Plugged into a USB 3.0 port, my file extractor script chugs along at 25.9 MB/s, taking about 18 minutes to transfer 28 GB of video data.
Splurging another eleven bucks for a second reader produces this setup:
After plugging both readers into adjacent USB 3.0 ports, the script transfers files at 46.6 MB/s and copies 28 GB in 10 minutes.
So, yes, the reader can handle two cards at once, but at half the speed.
Not life-changing, but it shows why I like measurements so much …