Any SD card formatted in FAT32 can be used with the M. We are not aware of any incompatibilities so far.

Special certifications for increased speed are not necessary and are more likely to cause errors and faults.

SD XC cards (exFAT) with higher access speeds cannot be formatted in FAT32 and are therefore not suitable.

Since there are no large data transfers necessary with the M, a simple inexpensive SD HC card is completely sufficient.