The Dell Precision 7770 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 and 3.0 x4 PCIe NVMe Solid State Drives and can be set up as RAID0 or RAID1)