The dome part of the original Mercedes mount is smooth. The aftermarket mounts which failed for me after 30k miles had a fluted dome like the ones pictured in the ********az catalog. (actually they did not work properly from the beginning with all those rattling noises but I did find that out until I replaced them)
From what I an tell, Febi is a division of Bilstein that makes parts for folks who want to save a little money up front and don't mind doing the same job over and over again. It has cost and will cost me over 600 bucks to find that out! ($150 or so for the motor mounts and $50 for a Febi belt tensioner shock that lasted about 5K miles plus my time to the job over again). On my 300SD I replaced the guide rod mounts with Febi guide rod mounts and was shocked to find that I can no longer get enough castor adjustment to meet the alignment specs (thats another $150 not counting the cost of the original parts I will have to use when I do the job the second time...and the installation time and the cost of a second alignment to get the car to steer properly .
I am not saying that all aftermarket parts are inferior. In fact I buy aftermarket parts most of the time. From my experience Bosch remanufactured starters and alternators are as good as what comes in a Mercedes box and Bilstein shocks are the same as originals. Lemforder parts seem to be fine.
But I have experience that is bought and paid for and the based on that I think that Febi parts are junk.
Spend a few extra bucks and get "original ersatzteile" for your job and you will save money in the long run.

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL