Pci Express Specifications Direct

| Form Factor | Lanes | Use Case | Hot-plug | |-------------|-------|----------|-----------| | | x1, x4, x8, x16 | Desktops, servers | No | | M.2 (Key M) | x2, x4 | NVMe SSDs, Wi-Fi | No | | M.2 (Key E) | x1 | Bluetooth/Wi-Fi cards | No | | U.2 (SFF-8639) | x4 | Enterprise SSDs | Yes | | ExpressCard | x1 | Laptop expansion | Yes | | Thunderbolt 3/4 | x4 | External enclosures | Yes | | OCuLink (SFF-8611) | x4/x8 | External GPU/storage | Yes | | CEM (Add-in card) | up to x16 | Graphics, accelerators | No |