The HP ZBook 17 G4 Mobile Workstation Comes in 2 Different Drive Options from HP and Supports up to 3 Drives. (Two 2.5" Drives and/or One M.2 NGFF (2280) Solid State Drive) or (One 2.5" Drive and/or Two M.2 NGFF (2280) Solid State Drives) Note: When the second M.2 Drive is installed, the second M.2 Drive occupies the 2.5" Drive bay. When the primary 2.5" Drive is installed, the primary 2.5" Drive occupies the M.2 Drive bay. (Both M.2 slots support SATA and PCIe NVMe Solid State Drives)