The Dell Vostro 15 7000 (7590) Laptop Supports Either 2 or 3 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 Two M.2 NGFF (2280) or (2230) Solid State Drives) or (Two M.2 NGFF (2280) or (2230) Solid State Drives 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. M.2 slot 1 (SSD1) supports M.2 (2280) Drives only. M.2 slot 2 (SSD2) supports M.2 (2280) and (2230) Drives by moving the drive mounting bracket to accommodate the form factor. If installing a M.2 Drive in slot 2, you will need the M.2 Drive thermal cooling plate p/n 6P587 for installation. If installing a 2.5" Drive in models with the smaller 56Whr battery, you will need the 2.5" Drive caddy p/n 1PMFC and Drive cable p/n H6KPW for installation. (M.2 slot 1 (SSD1) supports PCIe NVMe Drives only and M.2 slot 2 (SSD2) supports SATA and PCIe NVMe Drives)