From Mach Xtreme:

The MX-ES USB3.0 Series utilizes hand-selected top performance Single Level Cell (SLC) NAND to offer extreme performance and endurance over Multi-Level Cell (MLC) NAND, which is typically used in other USB3.0 pendrives. Changing the NAND components from MLC to SLC significantly increases the performance and longevity of MX-ES Ultra flash drive.

These USB3.0 flash pendrives are much more durable and reliable and are built to endure severe operating environments such as extreme cold and hot temperatures, continuous vibration, high shock impact, intensive read-write cycles etc. Such features are essential to users that require a more robust and rugged digital storage option to ensure repeatable and reliable operation. With selected, powerful SLC flash and proven design; the MX-ES Ultra Series drastically outperforms standard ES pendrives.