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
The M.2 interface
M.2 - Wikipedia
M.2 - Wikipedia
The M.2 interface
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