Hello there.
I bought Sandisks EXTREME MicroSDXC UHS-I C10 U3 64GB
but it does not even show on the interface.
is there some kind of a “supported SD’s” list?
Access your router by Winbox, open System —> Disk.
Do you see microSD disk there?
that’s what i ment by “its not visible in interface” 
i can’t see any sign of it.
Seems to be CCR supports only 32 and bellow microsd…I also was not able to use 64gb microsd.
Today I was finally able to see this router with my own eyes ( and hands )
we tried to insert 4GB memory card - no result …
but wen i inserted 32 GB … it suddenly apeared, tried to replace it again with 64GB - no result … back to 32GB - silence… nothing… tried to get 0.5 mm of th card out to see if it connects - nothing…
could it be hardware failure ?
Tonight ill try to reboot the router with SD in it.
After a reboot … 32GB card is accesable.
tomorrow I will try again with the 64GB
Accessable … but not usable 
I can’t format it properly … formating to FAT32 resulted in rubbish in catalogue DISK2 in FILES menu.
after that i tried to format it to ext3 … aaand the card is gone again. Reboot does not help.
can someone at least show me direction where to look for the cause of such behaviour ?
OK. Case is resolved.
64GB is normally supported, BUT there is no HOTPLUGG feature, so i had to:
insert the card
reboot the router
format the card
reboot the router
and then - the card was fully accesable.
Hello! Please tell which RouterOS version do you use on CCR?
I face the same issue with microSD card 16Gb. When my filesize reaches 390-400Mb, the read/write speed extremely falls down to zero.