An M.2 SSD is “keyed” to prevent insertion of a card connector (male) to an incompatible socket (female) on the host. The M.2 specification identifies 12 key IDs on the module card and socket interface but M.2 SSDs typically use three common keys: B, M, and B+M
M.2 vs NVMe vs. 2.5 vs. U.2 SSDs
M.2 Connector Guide on Keys and Sockets for SSDs
Overview of M.2 SSDs
The M.2 interface
What is the meaning of the keys of M.2 SSDs? - MEDION Community
How to know if the M.2 slots in my laptop is SATA or NVME (PCIE
M.2 - Wikipedia
What Is The M.2 Expansion Slot? The Future Of Compact, Robust
M.2 For Hackers – Connectors
What Else Is An M.2 WiFi Slot Good For?
2 Types of M.2 SSDs: SATA and NVMe - Kingston Technology