Feels like space alien skin.
The material on this jacket is very odd and very cool. Kind of like a gossamer alien membrane that stretches and weighs less than a piece of toast. I fully expected that it would not keep me dry in the Pacific Northwest drizzle, or that it would tear when I pulled on it.
After a number or rides this Sottile has become my favorite shell. I don't believe it's completely waterproof but highly water resistant. Also breathes and keeps out the wind. I stuff it in my jersey anytime there is any chance of rain.
The one "downside" is the steep price for 3 ounces of plastic. But hey! Alien skin ain't cheap. :)