All about SanDisk's microSD cards with the new A1 speed class - HardwareZone.com.sg
Are high-speed/high-capacity (A1, A2, U3) microSD cards worth it for Android? With Black Friday and Cyber Monday deals coming up, I (re)tested 5 of those and 2 older ones in 3 quite
16GB Sandisk Ultra SD/MicroSD Memory Card Class 10 A1 - Adapter Included - OSA Electronics
A2-class microSD cards offer no better performance for the Raspberry Pi | Jeff Geerling