SanDisk just took the wraps off of its new 128GB Ultra microSD card. On sale today for your favorite microSDXC-enabled phone or tablet, the card offers twice the storage of current cards, making it the largest-capacity microSD card on the market. Doubling up the storage space wasnt easy, in fact SanDisk used custom manufacturing to stack 16 memory dies — each thinner than a human hair — within each card.