The Dell Precision 3541 Mobile Workstation Supports Single and Dual Drive Configurations and is Available in Two Variants, Depending on the Battery Installed. (Dual Drive Variant - One 2.5" Drive and/or One M.2 (2280) or (2230) Drive with the Smaller 3/4-cell 51Whr/68Whr Battery Installed) or (Single Drive Variant - One M.2 (2280) or (2230) 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 2230 drive uses a adapter bracket p/n 07HMH to accommodate for the larger M.2 slots form factor. The 2.5" drives require caddy p/n ND8N9 and cable p/n 78RF8 for installation. The M.2 drives require the thermal support bracket p/n 85J62 for installation.