The HP ZBook 17 G3 Mobile Workstation Supports up to 4 Drives. (Two 2.5" Solid State Drives or Hard Drives and/or Two M.2 NGFF (2280) Solid State Drives) Note: If the primary or secondary 2.5" Drive was not installed from HP, you will need the 2.5" Drive hardware kit p/n 848351-001 (Includes: 2.5" Drive bracket, connector and screws) for installation. (Both M.2 slots support SATA and PCIe NVMe Solid State Drives)