It has different and changing profile - depends on the tack you are sailing. Company says that they look it up on fishes flippers and planes wings, which are also not symmetrical.
Because of this idea, we got about 20%
shorter fins then normal. I sailed my 7.6 sail
with 32cm fin today!
I can't say much, cause wind was so so, but the first impression is pretty nice!
Gutek (SmartFins, http://www.oddech.pl/)