"One of the most exciting additions to the Raspberry Pi 5 feature set is the single-lane PCI Express 2.0 interface. Intended to support fast peripherals, it is exposed on a 16-pin, 0.5mm pitch FPC connector on the left-hand side of the board.
From early 2024, we will be offering a pair of mechanical adapter boards which convert between this connector and a subset of the M.2 standard, allowing users to attach NVMe SSDs and other M.2-format accessories."