They are actualy vertical "wings" that mount to the side/on top of the ski. different from the cooling fins. Simmons skis are quite thin and there is not much of a "keal" When you get in the deep powder the skis sometimes want to slide sideways through the powder. The vertical wing gives the powder something to push against, you turn instead of slide. I just got a pair from simmions. I could not find them on thier website, but they do have them just ask I paid $20. I really don't know why the're not more popular. My friend sold me a pair of simmions with a set wings he made out of some of some aluminum angle iron. They really helped the ski turn in the powder but ended up bending when I hit a big bump/rock. The simmons version should flex with the ski (I hope). and for $20 it not really worth the time to try and make your own.
I'll try to get some pics of them.