As some motherboard host connectors only accommodate M-key SSDs and others only B-key ones, a popular pin design for M.2 SSDs these days is the B+M key, which allows for the best possible compatibility over various platforms.
However, if an M.2 SSD is not properly inserted (e.g., if it’s inserted upside down), the SSD may get burnt.
If you are uncertain about the correct direction at which your SSD should be installed, please refer to your user’s guide or contact your vendor for help.
Note: The below picture illustrates one possible scenario. The actual situation will depend on your device protocol.
