The Lenovo ThinkBook 15 G2 ITL Laptop Comes in 2 Different Drive Options Depending on the Battery Installed and Supports Single and Dual Drive Configurations. (Models with the Smaller 3-cell 45Whr Battery Installed: One 2.5" Solid State Drive or Hard Drive and/or One M.2 NGFF (2280) or (2242) Solid State Drive) or (Models with the Larger 4-cell 60Whr Battery Installed: Two M.2 NGFF (2280) or (2242) Solid State Drives) Note: Models that have the larger 60Whr battery installed do not support 2.5" Drives due to the larger battery occupying the 2.5" Drive bay. The M.2 (2242) Drive uses a adapter bracket p/n 5B40S22042 to accommodate for the larger M.2 (2280) slots. If the 2.5" Drive was not installed in models with the smaller 45Whr battery, you will need the 2.5" Drive bracket p/n 5B40S22041 and cable p/n 5C10S30187 for installation. (The primary M.2 slot SSD1 supports Generation 4.0 x4 and 3.0 x4 PCIe NVMe Drives and the secondary M.2 slot SSD2 supports Generation 3.0 x4 PCIe NVMe Drives)