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product description says OSX support, so its probably bootable. Its really down to if the card is AHCI compliant. Besides, Amazon has a great return policy, so if it doesnt work you wont be out anything other than your time.
[doublepost=1493864959][/doublepost]looks like its fine, one of the reviews:

5.0 out of 5 starsFive Stars
BySlash-2CPUon April 18, 2016
Color: PCIe M.2 (M-Key)|Verified Purchase
Works fine in a 2010 Mac Pro with a 512GB SM951, AHCI version. Bootable as well.
 
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They have one model that takes b key M.2 (2 blades) and has 2 SATA ports. The other version take m key blades - but I really want to use the one that holds multiple blades. That is my concern, I have not seen anyone use the non-samsung 941/951 blades and it work.
 
ah i see what you mean. Silly Amazon with the way they list things. Its laid out like it might be a variation of the same product but it could be something else entirely. not really sure if there's any way to specifically know what the hardware of the card is with the way they list it.
 
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