Nextor is an evolution of MSX-DOS 2 natively supporting FAT16 partitions up to 4GB, and can have 4 partitions per SD card. 128KB of Mapper is required on the minimum to use Nextor with access to sub-directories, less than 128K mapper only allows the use of the MSXDOS1 kernel, limiting partitions with FAT12 and maximum 16MB per partition.
eBay