Maps updates require 32GB sdcard formatted in FAT32, can’t be lower or bigger.
SDCARD must be SDHC only (SDXC might not working).
For firmware and other scripts 4GB should be more than enough.
For MMI 3G Plus (Europe) we recommend Samsung EVO+ 32GB sdcard – as other brands might not have enough space for map update.. even if it’s 32GB sdcard, they have different capacity – around 28,6GB, Samsung EVO+ got around 29,5GB of real capacity.
Other MMIs standard 32GB sdcard should be fine and we recommend to use Kingson Canvas & Samsung EVO+; they are tested by us and we can confirm all updates go straight forward!
However newest maps update for Europe require largest SD CARD’s so you need to use 64GB – please take a look here how to format 64GB SD to FAT32 (click).