Shan Found this
What is the difference between SanDisk Ultra and Extreme?
The
Extreme card uses
Ultra DMA technology to achieve read and write speeds that are double the speed of an
Ultra card.
Ultra cards read and write at a maximum of 30 MB per second, except for the 2GB version which only has a 15 MB per second maximum.
Extreme cards read and write at a maximum of 60 MB per second.