The Dell XPS 7590 Laptop Supports Either 1 or 2 Drives Depending on the Battery Installed. (One 2.5" Solid State Drive or Hard Drive with the Smaller 3-cell 56Whr Battery Installed and/or One M.2 NGFF (2280) or (2230) Solid State Drive) or (One M.2 NGFF (2280) or (2230) Solid State Drive with the Larger 6-cell 97Whr Battery Installed) Note: Models that have the larger 97Whr battery installed do not support 2.5" Drives due to the larger battery occupying the 2.5" Drive bay. The M.2 (2280) Solid State Drive has a unique thermal Plate and cannot be Interchanged with the (2230) Solid State Drive thermal Plate. If replacing the M.2 (2230) Drive for a M.2 (2280) Drive, you will need the M.2 (2280) Drive thermal plate p/n 90Y66 for installation. If Installing a 2.5" Drive in models with the smaller 56Whr battery installed, you will need the 2.5" Drive caddy p/n 3FDY3 and rubber rails p/n 3XYT5 and cable p/n XDYGX for installation. (The M.2 slot supports SATA and PCIe NVMe Solid State Drives)