I saw it online at Kiefer's. They claim it has extra room in the back to allow for long hair. I have one silicone cap, but it's a hassle because it doesn't really stretch enough for me to get all of my hair stuffed in. (Of course, I may just have a big head and I'm just blaming it all on the hair.) Needless to say, I just tend to use and abuse latex caps because they offer just a little more stretch. I'd like to switch back to silicone, but I'm curious if anyone has given this a try.
