The MacBook Air (2012) has an SD card slot that is rated at Revision 2 of the SD card slot.
https://www.sdcard.org/consumers/speed/bus_speed
About this Mac -> More Info -> System Report -> Card Reader:
Vendor ID: 0x05ac Product ID: 0x8404 Revision: 2.00 Serial Number: 310
Bus Interface: High Speed Card Type: SD, SDHC and SDXC Bus Speed: 25MB/s Spec Version: 2.00