<p>I have a Monoprice Select Mini v2 and it came with a 256 MB SD card. I have a bunch of 16 GB cards. I have made sure that the new SD card has a FAT32 filesystem. I copy the gcode file onto this card and when I put it in the printer, it can't find any files!</p>

<p>And yes, the file is at the root level of the filesystem and it uses the proper naming convention. The file works on the old card.</p>

<p>Since the old card still works, this isn't an emergency, but I want to have a backup and I don't have any other cards that small.</p>

The maximum size is 32 GB, however using microSD has a little disadvantage:
The microSD adapter and Micro memory are wrong assembled and the chip are unable to be read.
Solution: stick with a tape adhesive to keep Micro memory and SD adapter well aligned
The SD adapter can't be read on the 3D printer
Solution: Add an extra tape adhesive over the SD adapter just like sticker, to make tight the assembly inside the reader.
Clean the contacts of the SD adapter, normally has the same issue like nintendo cartridge.
I´m planning to get a bunch of SD cards instead microSD's, none of SD 8 GB and 16 GB are failing due wrong contact assembly.