The Dell Precision 7780 Mobile Workstation Supports up to 3 or 4 Drives Depending on the Battery Installed. (Four M.2 NGFF (2280) Solid State Drives with the Smaller 6-cell 93Whr Battery Installed) or (Three M.2 NGFF (2280) Solid State Drives with the Larger 6-cell 83Whr Battery Installed) Note: Models that have the larger 6-cell 83Whr battery installed do not support the 4th M.2 Drive in slot 2 (SSD-2) due to the larger battery occupying the M.2 Drive bay. M.2 slot 5 (SSD-5) supports M.2 (2230) Drives in the removable drive carrier. M.2 Slot 2 (SSD-2) and slot 3 (SSD-3) and Slot 4 (SSD-4) do not support M.2 (2230) Drives, only M.2 (2280) Drives. (All Four M.2 slots support Generation 4.0 x4 PCIe NVMe Solid State Drives and can be set up as RAID-0, RAID-1, RAID-5 or RAID-10)