M.2 SSD B+M Key - Meaning and will it be limited?

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Hi all,
I'm looking at purchasing a Samsung SSD - 850 Evo M.2. (http://www.amazon.com/Samsung-850-EVO-3-5-Inch-MZ-N5E500BW/dp/B00TGIW1XG)

It has B + M Notches, but i need a PCIE converter so I'm looking at this:

http://www.amazon.com/gp/product/B00MYCQP38

It states it will fit ONLY M Key not B key. Does this mean it will not work? Or if it does, does this mean it will be limited/slowed down?

I've seen this post as well: http://www.tomshardware.com/answers/id-2366078/ssd-key.html

but it doesn't seem to narrow it down.

Thanks!

 

[drtweak]

A M SSD Key will NOT fit in a B Key
A B SSD Key will NOT fit in a M Key
A M+B SDD Key WILL fit in EITHER a M key, B key, or M+B Key