ZTC Thunder Board NGFF M.2 M or B Key SSD to 18Pin. Replacement For Sandisk U100 Series SDSA5JK and ADATA XM11 all sizes SSD in Asus UX31 UX21 Zenbook. Model ZTC-AD003 Converts NGFF M.2 B or M Key SSD to 18Pin SSD. Supports 4 sizes of M.2 NGFF SSD 2230,2242,2260,2280 Works with PC , MAC and Linux Perfect fit to upgrade the drive in the Asus Zenbook UX31 UX21. **Does not Support M Key PCIe M.2 SSD**