Interesting. And potentially awesome, since I love my cool wings so much I just got a second one.

http://www.teamestrogen.com/prodDE_SHB.html

My concern is if it's "one size fits all," in which case I'd worry about it being too tight. I usually can't wear any kind of headband or bandana under my helmet on hot days because it gets too constricting. In fact I usually wind up loosening my helmet and sometimes I have to take the ponytail holder out of my hair. On the other hand, one would hope the cooling effect of the beanie would negate the feeling that I need to loosen everything on my head...

p.s. They should make a long sleeved jersey out of this fabric. And a sports bra, too.