I ordered the USB adapter for the 12" Retina MacBook. So far I've used it with various USB3 flash drives, Elgato Thunderbolt+ Drive, FirmTek diLite, and Areca 6 bay RAID box (ARC-5028T2).
The Areca (with both TB2 and USB3 ports) was ideal for cloning a MacBook Air using its Thunderbolt port and then connecting it to the MacBook's USB-C port to complete the migration.
The Areca (with both TB2 and USB3 ports) was ideal for cloning a MacBook Air using its Thunderbolt port and then connecting it to the MacBook's USB-C port to complete the migration.