The Dell Latitude 5501 Laptop Supports Single and Dual Drive Configurations Depending on the Battery Installed. (One 2.5" Solid State Drive or Hard Drive with the Smaller 3-cell 51Whr/68Whr 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 4-cell 97Whr Battery Installed) Note: Models that have the larger 4-cell 97Whr battery installed do not support 2.5" Drives due to the larger battery occupying the 2.5" Drive bay. The M.2 (2230) Drive uses a adapter bracket p/n 07HMH to accommodate for the larger M.2 (2280) slot. If the 2.5" Drive was not installed from Dell on models with the smaller 3-cell 51Whr/68Whr battery, you will need the 2.5" Drive caddy p/n ND8N9 and cable p/n 78RF8 for installation. If the M.2 Drive was not installed from Dell, you will need the M.2 thermal support bracket p/n 85J62 for installation. (The M.2 slot supports SATA and PCIe NVMe Solid State Drives)