The Dell Inspiron 15 7000 (7591) Laptop Supports up to 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 6-cell 97Whr battery installed do not support 2.5" Drives due to the larger battery occupying the 2.5" Drive bay. One M.2 slot supports both M.2 (2280) or (2230) Drives by moving the metal mounting bracket to accommodate the form factor. The other M.2 slot supports M.2 (2280) Drives only. If the 2.5" Drive was not Installed from Dell in models with the 56Whr battery, you will need the 2.5" Drive bracket p/n 3FDY3 and cable p/n DC2XG for installation. (Both M.2 slots supports PCIe NVMe Solid State Drives)