Magnet optical disc is one of optical discs. The size of discs is 3.5inch and there are a disk capacity of 128MB/230MB/540MB/640MB/1.3GB/2.6GB.
Originally, the disc need in writing time to be formated, written and verified, which is time-consuming and causes sever loss in performance. These years, a technology called overwrite improved the perfomance by enabling format unnecessary.
It has been quite popular in Japan.