Difference entre wdbmma0100hnc-wrsn et wd100efax

Hello everyone,
I was looking at buying 2 new 10to hard drives to replace mine in a DS214+ Nas.
When looking at it I found 2 models Wester digital, wdbmma0100hnc-wrsn and wd100efax.
The first one is much cheaper that second one but looking at it they really looks like they are the same one !
Would you know the difference ?
Many thanks for your help