The Acer Predator GX-791 Laptop Supports up to 4 Drives. (One 2.5" Solid State Drive or Hard Drive and/or Two M.2 NGFF (2280) Solid State Drives and/or One M.2 NGFF (2210) Solid State Drive) Note: M.2 slot 1 (SSD1) supports M.2 (2280) SATA and PCIe NVMe Drives. M.2 slot 2 (SSD2) supports M.2 (2210) SATA Drives only. M.2 slot 3 (SSD3) supports M.2 (2280) SATA Drives only. You can install a M.2 (2280) SATA Drive in slot 2 (SSD2) by using a adapter bracket p/n 33.Q04N5.001 to accommodate for the larger M.2 (2210) slot. If the 2.5" Drive was not installed from Acer, you will need the 2.5" Drive bracket and cable for installation.